ScreenWithMenuElements::StartTransitioning -> StartTransitioningScreen, to make searching

for it easier (vs. Transition::StartTransitioning).  (Trying to simplify tweening; this
may go back later.)

stepmania/src/ScreenJoinMultiplayer.cpp

@@ -253,7 +253,7 @@ void ScreenJoinMultiplayer::MenuStart( PlayerNumber pn )
 		return;
 	}
 	
-	this->StartTransitioning( SM_GoToNextScreen );
+	this->StartTransitioningScreen( SM_GoToNextScreen );
 }