Updatable views

Hi,

This is the patch for updatable views I've been able to come up with. A
nasty bug was just discovered in the upcoming Mammoth Replicator release
so I'm not sure if I'm going to have time to work more on it soon.

So, I'll appreciate if somebody else takes the responsability to fix the
remaining issues. I've put a lot of XXX's and some FIXME's. Some
functions are in need of some comments as well.

The new files are src/backend/rewrite/viewUpdate.c and
src/include/rewrite/viewUpdate.h. The third file, upd-views.sql, is
intended to be a new regression test. Extra points if the table therein
is completed correctly.

I haven't tested the array stuff at all.

Comments from Bernd and Jaime are especially welcome if I've broken
something that used to work on their patch :-)

--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.