pgsql: Revert addition of poorly-thought-out DUMP TIMESTAMP archive

Log Message:
-----------
Revert addition of poorly-thought-out DUMP TIMESTAMP archive entry,
which induced bug #1597 in addition to having several other misbehaviors
(like labeling the dump with a completion time having nothing to do with
reality).  Instead just print out the desired strings where RestoreArchive
was already emitting the 'PostgreSQL database dump' and
'PostgreSQL database dump complete' strings.

Modified Files:
--------------
    pgsql/src/bin/pg_dump:
        pg_backup_archiver.c (r1.106 -> r1.107)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_backup_archiver.c.diff?r1=1.106&r2=1.107)
        pg_dump.c (r1.406 -> r1.407)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/pg_dump/pg_dump.c.diff?r1=1.406&r2=1.407)