bug#6430: Emacs WINDOWS truncates exit status of processes to 8 bits

[Eli Zaretskii]

> From: Óscar Fuentes <ofv@wanadoo.es>
> Cc: npostavs@users.sourceforge.net,  6430@debbugs.gnu.org
> Date: Thu, 16 Jun 2016 19:56:48 +0200
> 
> cl.exe, for instance, uses the codes in winerror.h for reporting
> failures:
> 
> https://msdn.microsoft.com/en-us/library/ebh0y918.aspx

Those are just the normal error codes in disguise, and the ones
relevant to cl.exe are all below 255 (when the top 2 bits are
stripped).  So I see no problem here with the 8-bit limitation of the
status we report.