Fix dependency, when changing a function's argument/return type.

Fix dependency, when changing a function's argument/return type.

When a new base type is created using the old-style procedure of first
creating the input/output functions with "opaque" in place of the base
type, the "opaque" argument/return type is changed to the final base type,
on CREATE TYPE. However, we did not create a pg_depend record when doing
that, so the functions were left not depending on the type.

Fixes bug #14706, reported by Karen Huddleston.

Discussion: https://www.postgresql.org/message-id/20170614232259.1424.82774@wrigleys.postgresql.org