Returns the index of the parent of a given row.
Original signature is '- (NSInteger)parentRowForRow:(NSInteger)rowIndex'
Available in Mac OS X v10.5 and later.


- rowIndex (NSInteger)
- The index of a row in the receiver.

The index of the parent of the row at rowIndex. If the row at rowIndex is a root row, returns -1.

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