BOOST_PLAT platform macros

MinGW platform. Version number available as major, minor, and patch.

Symbol	Version
`__MINGW32__`	detection
`__MINGW64__`	detection
`__MINGW64_VERSION_MAJOR`, `__MINGW64_VERSION_MINOR`	V.R.0
`__MINGW32_VERSION_MAJOR`, `__MINGW32_VERSION_MINOR`	V.R.0

Symbol	Version
`!WINAPI_FAMILY`	detection
`WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP`	detection

Symbol	Version
`WINAPI_FAMILY == WINAPI_FAMILY_PHONE_APP`	detection

Symbol	Version
`WINAPI_FAMILY == WINAPI_FAMILY_APP`	detection
`WINAPI_FAMILY == WINAPI_FAMILY_PHONE_APP`	detection

Symbol	Version
`WINAPI_FAMILY == WINAPI_FAMILY_APP`	detection