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).

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