Fix a goofup from the recent sort consolidation patches.

- Subtractions in comparison functions could overflow the return type for
  64-bit pointers.  Make it right again.

- Add missing size arg to ia64 extable swap function.
Signed-off-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>