cmdutils: replace usages of "#ifdef __MINGW32__" with "#ifdef _WIN32" because...

cmdutils: replace usages of "#ifdef __MINGW32__" with "#ifdef _WIN32" because MSVC only defines _WIN32

With the previous patch, this should fix ticket #3580 as well.
Signed-off-by: John Peebles <johnpeeb@gmail.com>

cmdutils.h

@@ -30,7 +30,7 @@
 #include "libavformat/avformat.h"
 #include "libswscale/swscale.h"
 
-#ifdef __MINGW32__
+#ifdef _WIN32
 #undef main /* We don't want SDL to override our main() */
 #endif
 

ffplay.c

@@ -3635,7 +3635,7 @@ int main(int argc, char **argv)
         flags &= ~SDL_INIT_AUDIO;
     if (display_disable)
         SDL_putenv(dummy_videodriver); /* For the event queue, we always need a video driver. */
-#if !defined(__MINGW32__) && !defined(__APPLE__)
+#if !defined(_WIN32) && !defined(__APPLE__)
     flags |= SDL_INIT_EVENTTHREAD; /* Not supported on Windows or Mac OS X */
 #endif
     if (SDL_Init (flags)) {