Reset input redirection on screen change

It's possible for LUA to redirect input and not bring it back when screen is
ending (and there are existing bugs like this in Simply Love). Considering that
each screen is a separate entity, it seems like this shouldn't be possible and
each screen should handle redirection separately. Split redirection state per
each screen in the stack and clear it once screen is ending.

src/Screen.cpp

@@ -106,6 +106,9 @@ void Screen::EndScreen()
 {
 	this->PlayCommand( "End" );
 	m_bRunning = false;
+
+	m_InputCallbacks.clear();
+	m_DelayedCallbackRemovals.clear();
 }
 
 void Screen::Update( float fDeltaTime )