pg_dump doesn't properly honor -O for sequences

pg_dump -O apparently removes all instances of ALTER TABLE ... OWNER TO
from the output, but does not remove ALTER SEQUENCE ... OWNED BY from
the output.

Specifically this is with SERIAL sequences, which are dumped using the
ALTER SEQUENCE syntax (as of 8.2). Normal sequences are dumped using the
ALTER TABLE ... OWNER TO syntax, which properly honors -O.

Regards,
    Jeff Davis