Integrated David Ludwig's support for Windows RT

src/render/opengles2/SDL_render_gles2.c

@@ -1805,6 +1805,14 @@ GLES2_CreateRenderer(SDL_Window *window, Uint32 flags)
         return NULL;
     }
 
+#if __WINRT__
+    /* DLudwig, 2013-11-29: ANGLE for WinRT doesn't seem to work unless VSync
+     * is turned on.  Not doing so will freeze the screen's contents to that
+     * of the first drawn frame.
+     */
+    flags |= SDL_RENDERER_PRESENTVSYNC;
+#endif
+
     if (flags & SDL_RENDERER_PRESENTVSYNC) {
         SDL_GL_SetSwapInterval(1);
     } else {