gitian: bump faketime to something more recent

This helps in file views where binaries are sorted by time

contrib/gitian-descriptors/gitian-linux.yml

@@ -16,7 +16,7 @@ packages:
 - "bsdmainutils"
 - "binutils-gold"
 - "libstdc++6-4.6-pic"
-reference_datetime: "2013-06-01 00:00:00"
+reference_datetime: "2015-06-01 00:00:00"
 remotes:
 - "url": "https://github.com/bitcoin/bitcoin.git"
   "dir": "bitcoin"

contrib/gitian-descriptors/gitian-osx-signer.yml

@@ -7,7 +7,7 @@ architectures:
 packages:
 - "libc6:i386"
 - "faketime"
-reference_datetime: "2013-06-01 00:00:00"
+reference_datetime: "2015-06-01 00:00:00"
 remotes: []
 files:
 - "bitcoin-osx-unsigned.tar.gz"

contrib/gitian-descriptors/gitian-osx.yml

@@ -18,7 +18,7 @@ packages:
 - "libcap-dev"
 - "libz-dev"
 - "libbz2-dev"
-reference_datetime: "2013-06-01 00:00:00"
+reference_datetime: "2015-06-01 00:00:00"
 remotes:
 - "url": "https://github.com/bitcoin/bitcoin.git"
   "dir": "bitcoin"

contrib/gitian-descriptors/gitian-win.yml

@@ -18,7 +18,7 @@ packages:
 - "g++-mingw-w64"
 - "nsis"
 - "zip"
-reference_datetime: "2013-06-01 00:00:00"
+reference_datetime: "2015-06-01 00:00:00"
 remotes:
 - "url": "https://github.com/bitcoin/bitcoin.git"
   "dir": "bitcoin"