doc: Add release notes for 0.13.1 release

doc/release-notes/release-notes-0.13.1.md

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+Bitcoin Core version 0.13.1 is now available from:
+
+  <https://bitcoin.org/bin/bitcoin-core-0.13.1/>
+
+This is a new minor version release, including activation parameters for the
+segwit softfork, various bugfixes and performance improvements, as well as
+updated translations.
+
+Please report bugs using the issue tracker at github:
+
+  <https://github.com/bitcoin/bitcoin/issues>
+
+To receive security and update notifications, please subscribe to:
+
+  <https://bitcoincore.org/en/list/announcements/join/>
+
+Compatibility
+==============
+
+Microsoft ended support for Windows XP on [April 8th, 2014](https://www.microsoft.com/en-us/WindowsForBusiness/end-of-xp-support),
+an OS initially released in 2001. This means that not even critical security
+updates will be released anymore. Without security updates, using a bitcoin
+wallet on a XP machine is irresponsible at least.
+
+In addition to that, with 0.12.x there have been varied reports of Bitcoin Core
+randomly crashing on Windows XP. It is [not clear](https://github.com/bitcoin/bitcoin/issues/7681#issuecomment-217439891)
+what the source of these crashes is, but it is likely that upstream
+libraries such as Qt are no longer being tested on XP.
+
+We do not have time nor resources to provide support for an OS that is
+end-of-life. From 0.13.0 on, Windows XP is no longer supported. Users are
+suggested to upgrade to a newer version of Windows, or install an alternative OS
+that is supported.
+
+No attempt is made to prevent installing or running the software on Windows XP,
+you can still do so at your own risk, but do not expect it to work: do not
+report issues about Windows XP to the issue tracker.
+
+From 0.13.1 onwards OS X 10.7 is no longer supported. 0.13.0 was intended to work on 10.7+, 
+but severe issues with the libc++ version on 10.7.x keep it from running reliably. 
+0.13.1 now requires 10.8+, and will communicate that to 10.7 users, rather than crashing unexpectedly.
+
+Notable changes
+===============
+
+Segregated witness soft fork
+----------------------------
+
+Segregated witness (segwit) is a soft fork that, if activated, will
+allow transaction-producing software to separate (segregate) transaction
+signatures (witnesses) from the part of the data in a transaction that is
+covered by the txid. This provides several immediate benefits:
+
+- **Elimination of unwanted transaction malleability:** Segregating the witness
+  allows both existing and upgraded software to calculate the transaction
+  identifier (txid) of transactions without referencing the witness, which can
+  sometimes be changed by third-parties (such as miners) or by co-signers in a
+  multisig spend. This solves all known cases of unwanted transaction
+  malleability, which is a problem that makes programming Bitcoin wallet
+  software more difficult and which seriously complicates the design of smart
+  contracts for Bitcoin.
+
+- **Capacity increase:** Segwit transactions contain new fields that are not
+  part of the data currently used to calculate the size of a block, which
+  allows a block containing segwit transactions to hold more data than allowed
+  by the current maximum block size. Estimates based on the transactions
+  currently found in blocks indicate that if all wallets switch to using
+  segwit, the network will be able to support about 70% more transactions. The
+  network will also be able to support more of the advanced-style payments
+  (such as multisig) than it can support now because of the different weighting
+  given to different parts of a transaction after segwit activates (see the
+  following section for details).
+
+- **Weighting data based on how it affects node performance:** Some parts of
+  each Bitcoin block need to be stored by nodes in order to validate future
+  blocks; other parts of a block can be immediately forgotten (pruned) or used
+  only for helping other nodes sync their copy of the block chain.  One large
+  part of the immediately prunable data are transaction signatures (witnesses),
+  and segwit makes it possible to give a different "weight" to segregated
+  witnesses to correspond with the lower demands they place on node resources.
+  Specifically, each byte of a segregated witness is given a weight of 1, each
+  other byte in a block is given a weight of 4, and the maximum allowed weight
+  of a block is 4 million.  Weighting the data this way better aligns the most
+  profitable strategy for creating blocks with the long-term costs of block
+  validation.
+
+- **Signature covers value:** A simple improvement in the way signatures are
+  generated in segwit simplifies the design of secure signature generators
+  (such as hardware wallets), reduces the amount of data the signature
+  generator needs to download, and allows the signature generator to operate
+  more quickly.  This is made possible by having the generator sign the amount
+  of bitcoins they think they are spending, and by having full nodes refuse to
+  accept those signatures unless the amount of bitcoins being spent is exactly
+  the same as was signed.  For non-segwit transactions, wallets instead had to
+  download the complete previous transactions being spent for every payment
+  they made, which could be a slow operation on hardware wallets and in other
+  situations where bandwidth or computation speed was constrained.
+
+- **Linear scaling of sighash operations:** In 2015 a block was produced that
+  required about 25 seconds to validate on modern hardware because of the way
+  transaction signature hashes are performed.  Other similar blocks, or blocks
+  that could take even longer to validate, can still be produced today.  The
+  problem that caused this can't be fixed in a soft fork without unwanted
+  side-effects, but transactions that opt-in to using segwit will now use a
+  different signature method that doesn't suffer from this problem and doesn't
+  have any unwanted side-effects.
+
+- **Increased security for multisig:** Bitcoin addresses (both P2PKH addresses
+  that start with a '1' and P2SH addresses that start with a '3') use a hash
+  function known as RIPEMD-160.  For P2PKH addresses, this provides about 160
+  bits of security---which is beyond what cryptographers believe can be broken
+  today.  But because P2SH is more flexible, only about 80 bits of security is
+  provided per address. Although 80 bits is very strong security, it is within
+  the realm of possibility that it can be broken by a powerful adversary.
+  Segwit allows advanced transactions to use the SHA256 hash function instead,
+  which provides about 128 bits of security  (that is 281 trillion times as
+  much security as 80 bits and is equivalent to the maximum bits of security
+  believed to be provided by Bitcoin's choice of parameters for its Elliptic
+  Curve Digital Security Algorithm [ECDSA].)
+
+- **More efficient almost-full-node security** Satoshi Nakamoto's original
+  Bitcoin paper describes a method for allowing newly-started full nodes to
+  skip downloading and validating some data from historic blocks that are
+  protected by large amounts of proof of work.  Unfortunately, Nakamoto's
+  method can't guarantee that a newly-started node using this method will
+  produce an accurate copy of Bitcoin's current ledger (called the UTXO set),
+  making the node vulnerable to falling out of consensus with other nodes.
+  Although the problems with Nakamoto's method can't be fixed in a soft fork,
+  Segwit accomplishes something similar to his original proposal: it makes it
+  possible for a node to optionally skip downloading some blockchain data
+  (specifically, the segregated witnesses) while still ensuring that the node
+  can build an accurate copy of the UTXO set for the block chain with the most
+  proof of work.  Segwit enables this capability at the consensus layer, but
+  note that Bitcoin Core does not provide an option to use this capability as
+  of this 0.13.1 release.
+
+- **Script versioning:** Segwit makes it easy for future soft forks to allow
+  Bitcoin users to individually opt-in to almost any change in the Bitcoin
+  Script language when those users receive new transactions.  Features
+  currently being researched by Bitcoin Core contributors that may use this
+  capability include support for Schnorr signatures, which can improve the
+  privacy and efficiency of multisig transactions (or transactions with
+  multiple inputs), and Merklized Abstract Syntax Trees (MAST), which can
+  improve the privacy and efficiency of scripts with two or more conditions.
+  Other Bitcoin community members are studying several other improvements
+  that can be made using script versioning.
+
+Activation for the segwit soft fork is being managed using BIP9
+versionbits.  Segwit's version bit is bit 1, and nodes will begin
+tracking which blocks signal support for segwit at the beginning of the
+first retarget period after segwit's start date of 15 November 2016.  If
+95% of blocks within a 2,016-block retarget period (about two weeks)
+signal support for segwit, the soft fork will be locked in.  After
+another 2,016 blocks, segwit will activate.
+
+For more information about segwit, please see the [segwit FAQ][], the
+[segwit wallet developers guide][] or BIPs [141][BIP141], [143][BIP143],
+[144][BIP144], and [145][BIP145].  If you're a miner or mining pool
+operator, please see the [versionbits FAQ][] for information about
+signaling support for a soft fork.
+
+[Segwit FAQ]: https://bitcoincore.org/en/2016/01/26/segwit-benefits/
+[segwit wallet developers guide]: https://bitcoincore.org/en/segwit_wallet_dev/
+[BIP141]: https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki
+[BIP143]: https://github.com/bitcoin/bips/blob/master/bip-0143.mediawiki
+[BIP144]: https://github.com/bitcoin/bips/blob/master/bip-0144.mediawiki
+[BIP145]: https://github.com/bitcoin/bips/blob/master/bip-0145.mediawiki
+[versionbits FAQ]: https://bitcoincore.org/en/2016/06/08/version-bits-miners-faq/
+
+
+Null dummy soft fork
+-------------------
+
+Combined with the segwit soft fork is an additional change that turns a
+long-existing network relay policy into a consensus rule. The
+`OP_CHECKMULTISIG` and `OP_CHECKMULTISIGVERIFY` opcodes consume an extra
+stack element ("dummy element") after signature validation. The dummy
+element is not inspected in any manner, and could be replaced by any
+value without invalidating the script.
+
+Because any value can be used for this dummy element, it's possible for
+a third-party to insert data into other people's transactions, changing
+the transaction's txid (called transaction malleability) and possibly
+causing other problems.
+
+Since Bitcoin Core 0.10.0, nodes have defaulted to only relaying and
+mining transactions whose dummy element was a null value (0x00, also
+called OP_0).  The null dummy soft fork turns this relay rule into a
+consensus rule both for non-segwit transactions and segwit transactions,
+so that this method of mutating transactions is permanently eliminated
+from the network.
+
+Signaling for the null dummy soft fork is done by signaling support
+for segwit, and the null dummy soft fork will activate at the same time
+as segwit.
+
+For more information, please see [BIP147][].
+
+[BIP147]: https://github.com/bitcoin/bips/blob/master/bip-0147.mediawiki
+
+Low-level RPC changes
+---------------------
+
+- `importprunedfunds` only accepts two required arguments. Some versions accept
+  an optional third arg, which was always ignored. Make sure to never pass more
+  than two arguments.
+
+
+Linux ARM builds
+----------------
+
+With the 0.13.0 release, pre-built Linux ARM binaries were added to the set of
+uploaded executables. Additional detail on the ARM architecture targeted by each
+is provided below.
+
+The following extra files can be found in the download directory or torrent:
+
+- `bitcoin-${VERSION}-arm-linux-gnueabihf.tar.gz`: Linux binaries targeting
+  the 32-bit ARMv7-A architecture.
+- `bitcoin-${VERSION}-aarch64-linux-gnu.tar.gz`: Linux binaries targeting
+  the 64-bit ARMv8-A architecture.
+
+ARM builds are still experimental. If you have problems on a certain device or
+Linux distribution combination please report them on the bug tracker, it may be
+possible to resolve them. Note that the device you use must be (backward)
+compatible with the architecture targeted by the binary that you use.
+For example, a Raspberry Pi 2 Model B or Raspberry Pi 3 Model B (in its 32-bit
+execution state) device, can run the 32-bit ARMv7-A targeted binary. However,
+no model of Raspberry Pi 1 device can run either binary because they are all
+ARMv6 architecture devices that are not compatible with ARMv7-A or ARMv8-A.
+
+Note that Android is not considered ARM Linux in this context. The executables
+are not expected to work out of the box on Android.
+
+
+0.13.1 Change log
+=================
+
+Detailed release notes follow. This overview includes changes that affect
+behavior, not code moves, refactors and string updates. For convenience in locating
+the code changes and accompanying discussion, both the pull request and
+git merge commit are mentioned.
+
+### Consensus
+- #8636 `9dfa0c8` Implement NULLDUMMY softfork (BIP147) (jl2012)
+- #8848 `7a34a46` Add NULLDUMMY verify flag in bitcoinconsensus.h (jl2012)
+- #8937 `8b66659` Define start and end time for segwit deployment (sipa)
+
+### RPC and other APIs
+- #8581 `526d2b0` Drop misleading option in importprunedfunds (MarcoFalke)
+- #8699 `a5ec248` Remove createwitnessaddress RPC command (jl2012)
+- #8780 `794b007` Deprecate getinfo (MarcoFalke)
+- #8832 `83ad563` Throw JSONRPCError when utxo set can not be read (MarcoFalke)
+- #8884 `b987348` getblockchaininfo help: pruneheight is the lowest, not highest, block (luke-jr)
+- #8858 `3f508ed` rpc: Generate auth cookie in hex instead of base64 (laanwj)
+- #8951 `7c2bf4b` RPC/Mining: getblocktemplate: Update and fix formatting of help (luke-jr)
+
+### Block and transaction handling
+- #8611 `a9429ca` Reduce default number of blocks to check at startup (sipa)
+- #8634 `3e80ab7` Add policy: null signature for failed CHECK(MULTI)SIG (jl2012)
+- #8525 `1672225` Do not store witness txn in rejection cache (sipa)
+- #8499 `9777fe1` Add several policy limits and disable uncompressed keys for segwit scripts (jl2012)
+- #8526 `0027672` Make non-minimal OP_IF/NOTIF argument non-standard for P2WSH (jl2012)
+- #8524 `b8c79a0` Precompute sighashes (sipa)
+- #8651 `b8c79a0` Predeclare PrecomputedTransactionData as struct (sipa)
+
+### P2P protocol and network code
+- #8740 `42ea51a` No longer send local address in addrMe (laanwj)
+- #8427 `69d1cd2` Ignore `notfound` P2P messages (laanwj)
+- #8573 `4f84082` Set jonasschnellis dns-seeder filter flag (jonasschnelli)
+- #8712 `23feab1` Remove maxuploadtargets recommended minimum (jonasschnelli)
+- #8862 `7ae6242` Fix a few cases where messages were sent after requested disconnect (theuni)
+- #8393 `fe1975a` Support for compact blocks together with segwit (sipa)
+- #8282 `2611ad7` Feeler connections to increase online addrs in the tried table (EthanHeilman)
+- #8612 `2215c22` Check for compatibility with download in FindNextBlocksToDownload (sipa)
+- #8606 `bbf379b` Fix some locks (sipa)
+- #8594 `ab295bb` Do not add random inbound peers to addrman (gmaxwell)
+- #8940 `5b4192b` Add x9 service bit support to dnsseed.bluematt.me, seed.bitcoinstats.com (TheBlueMatt, cdecker)
+- #8944 `685e4c7` Remove bogus assert on number of oubound connections. (TheBlueMatt)
+- #8949 `0dbc48a` Be more agressive in getting connections to peers with relevant services (gmaxwell)
+
+### Build system
+- #8293 `fa5b249` Allow building libbitcoinconsensus without any univalue (luke-jr)
+- #8492 `8b0bdd3` Allow building bench_bitcoin by itself (luke-jr)
+- #8563 `147003c` Add configure check for -latomic (ajtowns)
+- #8626 `ea51b0f` Berkeley DB v6 compatibility fix (netsafe)
+- #8520 `75f2065` Remove check for `openssl/ec.h` (laanwj)
+
+### GUI
+- #8481 `d9f0d4e` Fix minimize and close bugs (adlawren)
+- #8487 `a37cec5` Persist the datadir after option reset (achow101)
+- #8697 `41fd852` Fix op order to append first alert (rodasmith)
+- #8678 `8e03382` Fix UI bug that could result in paying unexpected fee (jonasschnelli)
+- #8911 `7634d8e` Translate all files, even if wallet disabled (laanwj)
+- #8540 `1db3352` Fix random segfault when closing "Choose data directory" dialog (laanwj)
+- #7579 `f1c0d78` Show network/chain errors in the GUI (jonasschnelli)
+
+### Wallet
+- #8443 `464dedd` Trivial cleanup of HD wallet changes (jonasschnelli)
+- #8539 `cb07f19` CDB: fix debug output (crowning-)
+- #8664 `091cdeb` Fix segwit-related wallet bug (sdaftuar)
+- #8693 `c6a6291` Add witness address to address book (instagibbs)
+- #8765 `6288659` Remove "unused" ThreadFlushWalletDB from removeprunedfunds (jonasschnelli)
+
+### Tests and QA
+- #8713 `ae8c7df` create_cache: Delete temp dir when done (MarcoFalke)
+- #8716 `e34374e` Check legacy wallet as well (MarcoFalke)
+- #8750 `d6ebe13` Refactor RPCTestHandler to prevent TimeoutExpired (MarcoFalke)
+- #8652 `63462c2` remove root test directory for RPC tests (yurizhykin)
+- #8724 `da94272` walletbackup: Sync blocks inside the loop (MarcoFalke)
+- #8400 `bea02dc` enable rpcbind_test (yurizhykin)
+- #8417 `f70be14` Add walletdump RPC test (including HD- & encryption-tests) (jonasschnelli)
+- #8419 `a7aa3cc` Enable size accounting in mining unit tests (sdaftuar)
+- #8442 `8bb1efd` Rework hd wallet dump test (MarcoFalke)
+- #8528 `3606b6b` Update p2p-segwit.py to reflect correct behavior (instagibbs)
+- #8531 `a27cdd8` abandonconflict: Use assert_equal (MarcoFalke)
+- #8667 `6b07362` Fix SIGHASH_SINGLE bug in test_framework SignatureHash (jl2012)
+- #8673 `03b0196` Fix obvious assignment/equality error in test (JeremyRubin)
+- #8739 `cef633c` Fix broken sendcmpct test in p2p-compactblocks.py (sdaftuar)
+- #8418 `ff893aa` Add tests for compact blocks (sdaftuar)
+- #8803 `375437c` Ping regularly in p2p-segwit.py to keep connection alive (jl2012)
+- #8827 `9bbe66e` Split up slow RPC calls to avoid pruning test timeouts (sdaftuar)
+- #8829 `2a8bca4` Add bitcoin-tx JSON tests (jnewbery)
+- #8834 `1dd1783` blockstore: Switch to dumb dbm (MarcoFalke)
+- #8835 `d87227d` nulldummy.py: Don't run unused code (MarcoFalke)
+- #8836 `eb18cc1` bitcoin-util-test.py should fail if the output file is empty (jnewbery)
+- #8839 `31ab2f8` Avoid ConnectionResetErrors during RPC tests (laanwj)
+- #8840 `cbc3fe5` Explicitly set encoding to utf8 when opening text files (laanwj)
+- #8841 `3e4abb5` Fix nulldummy test (jl2012)
+- #8854 `624a007` Fix race condition in p2p-compactblocks test (sdaftuar)
+- #8857 `1f60d45` mininode: Only allow named args in wait_until (MarcoFalke)
+- #8860 `0bee740` util: Move wait_bitcoinds() into stop_nodes() (MarcoFalke)
+- #8882 `b73f065` Fix race conditions in p2p-compactblocks.py and sendheaders.py (sdaftuar)
+- #8904 `cc6f551` Fix compact block shortids for a test case (dagurval)
+
+### Documentation
+- #8754 `0e2c6bd` Target protobuf 2.6 in OS X build notes. (fanquake)
+- #8461 `b17a3f9` Document return value of networkhashps for getmininginfo RPC endpoint (jlopp)
+- #8512 `156e305` Corrected JSON typo on setban of net.cpp (sevastos)
+- #8683 `8a7d7ff` Fix incorrect file name bitcoin.qrc  (bitcoinsSG)
+- #8891 `5e0dd9e` Update bips.md for Segregated Witness (fanquake)
+- #8545 `863ae74` Update git-subtree-check.sh README (MarcoFalke)
+- #8607 `486650a` Fix doxygen off-by-one comments, fix typos (MarcoFalke)
+- #8560 `c493f43` Fix two VarInt examples in serialize.h (cbarcenas)
+- #8737 `084cae9` UndoReadFromDisk works on undo files (rev), not on block files (paveljanik)
+- #8625 `0a35573` Clarify statement about parallel jobs in rpc-tests.py (isle2983)
+- #8624 `0e6d753` build: Mention curl (MarcoFalke)
+- #8604 `b09e13c` build,doc: Update for 0.13.0+ and OpenBSD 5.9 (laanwj)
+- #8939 `06d15fb` Update implemented bips for 0.13.1 (sipa)
+
+### Miscellaneous
+- #8742 `d31ac72` Specify Protobuf version 2 in paymentrequest.proto (fanquake)
+- #8414,#8558,#8676,#8700,#8701,#8702 Add missing copyright headers (isle2983, kazcw)
+- #8899 `4ed2627` Fix wake from sleep issue with Boost 1.59.0 (fanquake)
+- #8817 `bcf3806` update bitcoin-tx to output witness data (jnewbery)
+- #8513 `4e5fc31` Fix a type error that would not compile on OSX. (JeremyRubin)
+- #8392 `30eac2d` Fix several node initialization issues (sipa)
+- #8548 `305d8ac` Use `__func__` to get function name for output printing (MarcoFalke)
+- #8291 `a987431` [util] CopyrightHolders: Check for untranslated substitution (MarcoFalke)
+
+Credits
+=======
+
+Thanks to everyone who directly contributed to this release:
+
+- adlawren
+- Alexey Vesnin
+- Anders Øyvind Urke-Sætre
+- Andrew Chow
+- Anthony Towns
+- BtcDrak
+- Chris Stewart
+- Christian Barcenas
+- Christian Decker
+- Cory Fields
+- crowning-
+- Dagur Valberg Johannsson
+- David A. Harding
+- Eric Lombrozo
+- Ethan Heilman
+- fanquake
+- Gaurav Rana
+- Gregory Maxwell
+- instagibbs
+- isle2983
+- Jameson Lopp
+- Jeremy Rubin
+- jnewbery
+- Johnson Lau
+- Jonas Schnelli
+- jonnynewbs
+- Justin Camarena
+- Kaz Wesley
+- leijurv
+- Luke Dashjr
+- MarcoFalke
+- Marty Jones
+- Matt Corallo
+- Micha
+- Michael Ford
+- mruddy
+- Pavel Janík
+- Pieter Wuille
+- rodasmith
+- Sev
+- Suhas Daftuar
+- whythat
+- Wladimir J. van der Laan
+
+As well as everyone that helped translating on [Transifex](https://www.transifex.com/projects/p/bitcoin/).