Clear out the reminants of EXTEND INDEX

Wow Tom, I'm impressed. You took the entire index system and turned it on
it's head, cleaned up most of my ugly bits and managed to remove most of the
stuff relating to extend in the process.

You missed a few spots though, so here a little patch to clear out the rest
(although maybe you're doing them as we speak, can't tell).

You also took care of my next idea, which was to allow IS NULL in the index
predicate.

Anyway, keep it up :)
--
Martijn van Oosterhout <kleptog(at)svana(dot)org>
http://svana.org/kleptog/
> It would be nice if someone came up with a certification system that
> actually separated those who can barely regurgitate what they crammed over
> the last few weeks from those who command secret ninja networking powers.