Remove ugly CopyTweening. This is too wildly incompatible with newer

XML features, where there's not necessarily any corrolation between elements
of different graphics.  This didn't work well, anyway: it'd apply the old tweening
queue to the new graphics, but they might have completely different animations.
This will cause transitions between NoteSkins to be more abrupt, but we don't
use that feature anyway.

stepmania/src/NoteField.cpp

@@ -162,17 +162,7 @@ void NoteField::Update( float fDeltaTime )
 	NoteDisplayCols *cur = SearchForSongBeat();
 
 	if( cur != LastDisplay )
-	{
-		/* The display has changed.  We might be in the middle of a step; copy any
-		 * tweens. */
-		if( LastDisplay )
-		{
-			cur->m_GhostArrowRow.CopyTweening( LastDisplay->m_GhostArrowRow );
-			cur->m_ReceptorArrowRow.CopyTweening( LastDisplay->m_ReceptorArrowRow );
-		}
-
 		LastDisplay = cur;
-	}
 
 	cur->m_ReceptorArrowRow.Update( fDeltaTime );
 	cur->m_GhostArrowRow.Update( fDeltaTime );