Document deprecated createuser option.
2dcd1578c4 left the --role option undocumented, which is
inconsistent with other deprecated options such as pg_dump's
--blobs and --no-blobs. This change adds --role back to
createuser's documentation and usage output and marks it as
deprecated.
Suggested-by: Peter Eisentraut
Reviewed-by: Michael Paquier
Discussion: https://postgr.es/m/
0e85c9e7-4804-1cdb-5a4a-
c72c328f9ad8%40enterprisedb.com