OSMesa draws upside down

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%40981

src/video/xbios/SDL_xbios.c

@@ -992,6 +992,9 @@ static int XBIOS_GL_MakeCurrent(_THIS)
 		return -1;
 	}
 
+	/* OSMesa draws upside down */
+	OSMesaPixelStore(OSMESA_Y_UP, 0);
+
 	return 0;
 }