verified it is also an issue om 5.1.0.Final

the mentioned function

@Override
public String getQuerySequencesString() {
    return "select relname from pg_class where relkind='S'";
}

exists in PostgreSQL81Dialect (in hibernate 5.1) and the the sql function pg_table_is_visible is also available in Postgres 8.1 (http://www.postgresql.org/docs/8.1/static/functions-info.html)