I think I may have discovered a reason why is_superuser is
intentionally undocumented. is_superuser is not updated if a role's
superuser attribute is changed by another session. Therefore,
is_superuser may show you an incorrect stale value.
Perhaps this can be fixed with a show_hook? Otherwise it's probably
best not to document a GUC that can show an incorrect value.
- Joe Koshakow
