Adds a subgroup to another group.
Original signature is '- (BOOL)addSubgroup:(ABGroup *)group'
Available in Mac OS X v10.2 and later.


- group (ABGroup)
- The group to add as a subgroup.

YES if successful; otherwise, NO.

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