UI,libobs,libobs-opengl,obs-ffmpeg: Remove unneeded cast in switches

Those casts were usually used to workaround switch warnings.

Also adds default to OBS frontend event switches that had this
workaround.

UI/window-basic-stats.cpp

@@ -22,13 +22,15 @@ void OBSBasicStats::OBSFrontendEvent(enum obs_frontend_event event, void *ptr)
 {
 	OBSBasicStats *stats = reinterpret_cast<OBSBasicStats *>(ptr);
 
-	switch ((int)event) {
+	switch (event) {
 	case OBS_FRONTEND_EVENT_RECORDING_STARTED:
 		stats->StartRecTimeLeft();
 		break;
 	case OBS_FRONTEND_EVENT_RECORDING_STOPPED:
 		stats->ResetRecTimeLeft();
 		break;
+	default:
+		break;
 	}
 }