pg_dump UDT/function dependency patch

Patch to put rudimentary dependency support into pg_dump. This addresses
the UDT/function order problem. Unfortunately, this is not a small patch so
I would prefer some debate about whether it should be applied 7.1.

* - Rudimentary support for dependencies in archives. Current
implementation
* uses dependencies to modify the OID used in sorting TOC
entries.
* This will NOT handle multi-level dependencies, but will
manage simple
* relationships like UDTs & their functions.
*
* - Treat OIDs with more respect (avoid using ints, use macros for
* conversion & comparison).