fix and question re: waitpid() under win32

So there are two issues:
1) win32_waitpid() in win32.c was unable to perform a nonblocking wait,
primarily due to:
2) WNOHANG not defined under win32.

Under Linux, WNOHANG is #defined to 1, so in reality you could probably
just check the flags arg against 1.  However, in the interest of
readability (if nothing else) I chose to #define WNOHANG 1 if it wasn't
already defined at the beginning of win32.c  You can then just set a
timeout value (0 or INFINITE) based on flags&WNOHANG.  Of course, you
must then check the return code for both WAIT_TIMEOUT in addition to
WAIT_FAILED.

I've included a patch to implement this.  I don't really like the
#define WNOHANG 1, but it's that or check against the constant 1...

			-Brian

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Brian Clarke
Applied MetaComputing LLC
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• fix and question re: waitpid() under win32 by Brian Clarke
• Re: fix and question re: waitpid() under win32 by Jarkko Hietaniemi