Kerberos includes (was Re: Port report: Fedora Core 3 x86_64)

I wrote:
>> [ concerning a discussion about Kerberos' com_err.h being in
>>   /usr/include/et/ on some systems ]

> Actually, I'm wondering why we directly include com_err.h at all.  At
> least in the version of <krb5.h> I have here, that file is included by
> krb5.h; so both backend/libpq/auth.c and interfaces/libpq/fe-auth.c
> compile just fine with #include <com_err.h> diked out.

After some digging in dusty old tarballs, I have learned that Kerberos 5
releases 1.0.* did indeed require a separate #include of com_err.h, but
in releases 1.1 and later krb5.h itself includes com_err.h and so
there's no need for a separate #include.

Kerberos 5 1.0.* includes serious known, never-patched vulnerabilities.
I can't believe that anyone is going to build PG 8.0 with krb5 1.0,
or that we need to be complicit in their trying to do so.

Accordingly, I think we should just avoid the whole problem of exactly
where com_err.h lives by removing the #includes for it as well as the
configure test for it.
        regards, tom lane