The output should always match openssl's, even for failed operations. Even for
a decrypt with broken padding, the output is always deterministic (and attemtps
to be constant-time).
Byte counts for SHA256, SHA512, SHA1 and RIPEMD160 must be 64 bits.
`size_t` has a different size per platform, causing divergent results
when hashing more than 4GB of data.
- Detect endian instead of stopping configure on big-endian
- Add `byteswap.h` and `endian.h` header for compatibility with
Windows and other operating systems that don't come with them
- Update `crypto/common.h` functions to use compat
endian header