bug#24613: Windows build with rsvg fails on newest MinGW

[Eli Zaretskii]

> Date: Tue, 04 Oct 2016 18:33:05 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 24613@debbugs.gnu.org
> 
> > From: Nikolay Kudryavtsev <nikolay.kudryavtsev@gmail.com>
> > Cc: 24613@debbugs.gnu.org
> > Date: Tue, 4 Oct 2016 17:58:50 +0300
> > 
> > what about MemoryBarrier?
> 
> Define away the one glib insist of giving us?  Like this:
> 
> #if __W32API_MAJOR_VERSION + (__W32API_MINOR_VERSION >= 18) >= 4
> # define MemoryBarrier glib_MemoryBarrier
> #endif
> #include <librsvg/rsvg.h>
> #undef MemoryBarrier
> 
> Does that work?

Never mind, I think I fixed this, on both emacs-25 and master.  Please
see if there's any fallout, or else close the bug report.

Thanks.