On 64-bit Windows, pid_t needs to be 64-bit large, i.e. intptr_t or 'long long'
or '__int64'.

This is because the return type of _spawnv* (when invoked with _P_NOWAIT) and
the argument of the _cwait function are 'intptr_t' (see [1][2]: "The return
value from an asynchronous _spawnvp or _wspawnvp (_P_NOWAIT or _P_NOWAITO
specified for mode) is the process handle."

On mingw, this is already the case. But on MSVC (and MSVC/clang), the 'pid_t'
type is nowhere defined. In this case, gnulib defines it through config.h.

[1] https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/spawnvp-wspawnvp
[2] https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/cwait


2020-08-23  Bruno Haible  <bruno@clisp.org>

	tests: Don't assume that pid_t fits in an 'int'.
	* tests/test-nonblocking-pipe-main.c (main): Use type 'pid_t' instead
	of 'int'.
	* tests/test-nonblocking-socket-main.c (main): Likewise.

	sys_types: Fix definition of pid_t on 64-bit MSVC.
	* m4/pid_t.m4: New file.
	* modules/sys_types (Files): Add it.
	* modules/dirent (Files): Likewise.
	* modules/fcntl-h (Files): Likewise.
	* modules/sched (Files): Likewise.
	* modules/signal-h (Files): Likewise.
	* modules/spawn (Files): Likewise.
	* modules/sys_stat (Files): Likewise.
	* modules/sys_wait (Files): Likewise.
	* modules/termios (Files): Likewise.
	* modules/unistd (Files): Likewise.