Renamed ReverseSelection to SelBackwards for consistency with other Sel* prroperties
Renamed mo_TempUndoItem to mo_ExtendedUndoItem for clarity
Renamed FlattenUndoStack to ConsolidateStack
Better UndoAvailable and RedoAvailable results
Start undo stack index at -1
Added CreateUndoItem method to cTextUndoStack
AddUndoItem now takes a cTextUndoStackItem object instead of series of properties
Added private StoreUndoItem method to push item onto end of undo stack
Replaced mLastUndoAction var with QueuedUndoItem object to hold state after last undoable action (for pushing to undo stack immediately before undoing)
Added optional AllowCancellation property to SetSelection in cwTextBox
	When TRUE, BeforeSelChange event will not be raised (good for internal selection changes that shouldn't be aborted by client)