Returns a value object whose key is the provided tag.
Original signature is '- (id)valueForTag:(long)tag client:(id)sender'
Available in Mac OS X v10.5 and later.
The value object. The returned object should be autoreleased.
- Available in Monobjc Bridge: 10.6 (For Mac OS X 10.6 and later), 10.5 (For Mac OS X 10.5 and later)