Merge branch 'ss/compat-bswap-revamp'

Clean-up compat/bswap.h mess.

* ss/compat-bswap-revamp:
  bswap.h: provide a built-in based version of bswap32/64 if possible
  bswap.h: remove optimized x86 version of bswap32/64
  bswap.h: always overwrite ntohl/ ntohll macros
  bswap.h: define GIT_LITTLE_ENDIAN on msvc as little endian
  bswap.h: add support for __BYTE_ORDER__