Re: [PATCH v4] mingw.c: Fix complier warnings for a 64 bit msvc

> Remove some complier warnings from msvc in compat/mingw.c for value
> truncation from 64 bit to 32 bit integers.
>
> Compiling compat/mingw.c under a 64 bit version of msvc produces
> warnings. An "int" is 32 bit, and ssize_t or size_t should be 64 bit
> long. Prepare compat/vcbuild/include/unistd.h to have a 64 bit type
> _ssize_t, when _WIN64 is defined and 32 bit otherwise.
>
> Further down in this include file, as before,ssize_t is defined as
> _ssize_t, if needed.