Add Screen::FirstUpdate().

stepmania/src/Screen.cpp

@@ -16,6 +16,7 @@
 
 Screen::Screen()
 {
+	m_FirstUpdate = true;
 }
 
 Screen::~Screen()
@@ -100,4 +101,11 @@ void Screen::SendScreenMessage( ScreenMessage SM, float fDelay )
 	QSM.SM = SM;
 	QSM.fDelayRemaining = fDelay;
 	m_QueuedMessages.Add( QSM );
-}
+}
+
+bool Screen::FirstUpdate()
+{ 
+	bool ret = m_FirstUpdate;
+	m_FirstUpdate = false;
+	return ret;
+}