ffplay: properly detect all window size changes

SDL_WINDOWEVENT_SIZE_CHANGED should be used instead of SDL_WINDOWEVENT_RESIZED
because SDL_WINDOWEVENT_RESIZED is only emitted if the resize happened due to
an external event.

Fixes ticket #8072.

Additional references:
https://bugzilla.libsdl.org/show_bug.cgi?id=4760
https://wiki.libsdl.org/SDL_WindowEventIDSigned-off-by: Marton Balint <cus@passwd.hu>

fftools/ffplay.c

@@ -3436,7 +3436,7 @@ static void event_loop(VideoState *cur_stream)
             break;
         case SDL_WINDOWEVENT:
             switch (event.window.event) {
-                case SDL_WINDOWEVENT_RESIZED:
+                case SDL_WINDOWEVENT_SIZE_CHANGED:
                     screen_width  = cur_stream->width  = event.window.data1;
                     screen_height = cur_stream->height = event.window.data2;
                     if (cur_stream->vis_texture) {