Returns the index of the currently highlighted menu item, or –1 if no menu item in the menu is highlighted.
Original signature is '- (NSInteger)highlightedItemIndex'
Available in Mac OS X v10.0 and later.


- Available in Monobjc Bridge: 10.6 (For Mac OS X 10.6 and later), 10.5 (For Mac OS X 10.5 and later)