POSIX specification:
http://www.opengroup.org/onlinepubs/9699919799/basedefs/sys_types.h.html
Gnulib module: sys_types
Portability problems fixed by Gnulib:
pid_t is not defined on some platforms:
MSVC 9.
size_t is not defined in this file on some platforms:
MSVC 9.
ssize_t is not defined on some platforms:
MSVC 9.
mode_t is not defined on some platforms:
MSVC 9.
Portability problems not fixed by Gnulib:
blksize_t and suseconds_t
are signed integer types that are wider than long:
glibc x32
This module, together with the module largefile, also defines the type
off_t to a 64-bit integer type on some platforms:
mingw (except mingw64), MSVC 9.