pg_dumpall: Add --sequence-data.

pg_dumpall: Add --sequence-data.

I recently added this option to pg_dump, but I forgot to add it to
pg_dumpall, too.  There's probably little use for it at the moment,
but we will need it if/when we teach pg_upgrade to use pg_dumpall
to dump the database schemas.

Oversight in commit 9c49f0e8cd.

Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/aBE8rHFo922xQUwh%40nathan