<rdar://problem/11689939>

Supporting a compact display syntax for ObjC pointers where 0x00.....0 is replaced by a much more legible "nil"
e.g. this would show:
(NSArray *) $2 = nil
instead of:
(NSArray *) $2 = 0x0000000000000000 <nil>

llvm-svn: 170161