pg_typeof() patch review

Hi,

Brendan Jurd submitted a patch to add a pg_typeof() builtin function:

http://archives.postgresql.org/pgsql-patches/2008-09/msg00029.php

I've reviewed the patch and it looks fine. An updated version is
attached, having made these changes:

1) Rebased to current CVS head

2) func.sgml: clarifying that the function returns an OID rather
than a string

3) catversion.h: updated catalog version with today's date

4) pg_proc.h: placed the new entry in numerical order (Note: Does
it matter how new pg_proc OIDs are assigned? I assume any
available OID - 826 in this case - is as good as any other?)

5) polymorphism.sql/polymorphism.out: added regression test for
the new function

I hope the attached patch is formatted ok - this is how it came
from Mercurial. I applied it using "patch -p 1".

This is my first review, so I welcome your feedback on whether
I'm doing it right.

Regards,
... kurt