Fix corner case for binary upgrade: extension functions in pg_catalog.

Fix corner case for binary upgrade: extension functions in pg_catalog.

Normally, pg_dump summarily excludes functions in pg_catalog from
consideration.  However, some extensions may create functions in pg_catalog
(adminpack already does that, and extensions for procedural languages will
likely do it too).  In binary-upgrade mode, we have to dump such functions,
or the extension will be incomplete after upgrading.  Per experimentation
with adminpack.