SDL_mixer patch for configure on msys

I have run into an issue with SDL_mixer using the most recent release.
configure.in now has EXTRA_CFLAGS defined as:

EXTRA_CFLAGS="$INCLUDE $BASE_CFLAGS"

My issue is that Visual Studio 2003 defines an environment variable
called INCLUDE, so the above line erroneously pulls in the path to
Visual Studio’s include directory during configure.

I’ve attached a patch that removes the $INCLUDE from $EXTRA_CFLAGS

thanks,