Cause pg_dump to emit a 'SET client_encoding' command at the start of

Cause pg_dump to emit a 'SET client_encoding' command at the start of
any restore operation, thereby ensuring that dumped data is interpreted
the same way it was dumped even if the target database has a different
encoding.  Per suggestions from Pavel Stehule and others.  Also,
simplify scheme for handling check_function_bodies ... we may as well
just set that at the head of the script.