Folded SDL_WINDOW_FULLSCREEN_EXCLUSIVE and SDL_WINDOW_FULLSCREEN_DESKTOP into a single SDL_WINDOW_FULLSCREEN flag

The fullscreen video mode used by the window can be used to determine whether it's in exclusive fullscreen or fullscreen desktop mode.

docs/README-winrt.md

@@ -340,7 +340,7 @@ int main(int argc, char **argv)
   
     if (SDL_Init(SDL_INIT_VIDEO) != 0) {
         return 1;
-    } else if (SDL_CreateWindowAndRenderer(0, 0, SDL_WINDOW_FULLSCREEN_DESKTOP, &window, &renderer) != 0) {
+    } else if (SDL_CreateWindowAndRenderer(0, 0, SDL_WINDOW_FULLSCREEN, &window, &renderer) != 0) {
         return 1;
     }