findoidjoins patch (was Re: [HACKERS] findoidjoins)

Tom Lane wrote:
> I'd be inclined to reproduce the original behavior. findoidjoins is
> pretty slow already, and I don't much want to slow it down more in order
> to provide info that's useless for the primary purpose.

Here's take two. It produces results similar to the previous version,
but using libpq and schema aware queries.

> use it for checking the stuff in pg_catalog. So I'm not at all sure why
> I made that note. Do you get a plausible set of joins out of your
> version?

Looks reasonable to me. I attached the outputs of findoidjoins and
make_oidjoins_check for review as well.

Please review and commit, or kick back to me if more work is needed.

Thanks,

Joe