Originally, the AdjustSync class always saved to disk, even in edit mode.

In edit mode, though, AdjustSync should only save to memory, giving the
user a chance to save later.  This change adds a SongChanged message
to the MessageManager.  Making the ScreenEdit class listen to this
message allows the AdjustSync class to mark a song as dirty rather than
saving it to disk when in edit mode.

R=steve chekoway

stepmania/src/ScreenEdit.cpp

@@ -763,6 +763,8 @@ void ScreenEdit::Init()
 
 	this->HandleScreenMessage( SM_UpdateTextInfo );
 	m_bTextInfoNeedsUpdate = true;
+
+	SubscribeToMessage( Message_SongChanged );
 }
 
 ScreenEdit::~ScreenEdit()
@@ -2365,6 +2367,15 @@ void ScreenEdit::ScrollTo( float fDestinationBeat )
 	m_soundChangeLine.Play();
 }
 
+void ScreenEdit::HandleMessage( const RString &sMessage )
+{
+	if( sMessage == MessageToString( Message_SongChanged ) )
+	{
+		SetDirty( true );
+	}
+	Screen::HandleMessage( sMessage );
+}
+
 static LocalizedString SAVE_SUCCESSFUL				( "ScreenEdit", "Save successful." );
 
 void ScreenEdit::HandleScreenMessage( const ScreenMessage SM )