cext: fix warnings when building for py3 on Windows...
cext: fix warnings when building for py3 on Windows
MSVC++ 14 now has standard int types that don't need to be redefined (I didn't
go back to see when they came along since the build system wants either 2008 or
2015), but doesn't have ssize_t. The FILE pointer in posixfile is only used on
python2.