Re: Role Attribute Bitmask Catalog Representation

> * int64 (C) to int8 (SQL) mapping for genbki.

That definitely should be a separate patch. Which can be committed much
earlier than the rest - even if we don't actually end up needing it for
this feature, it's still good to have it.

> * replace all role attributes columns in pg_authid with single int64 column
> named rolattr.
> * update CreateRole and AlterRole to use rolattr.
> * update all has_*_privilege functions to check rolattr.
> * builtin SQL function 'has_role_attribute' that takes a role oid and text
> name of the attribute as input and returns a boolean.

I think if we're going to do this - and I'm not yet convinced that
that's the best route, we should add returns all permissions a user
has. Right now that's quite easily queryable, but it won't be after
moving everything into one column. You'd need to manually use all has_*_
functions... Yes, you've added them already to pg_roles, but there's
sometimes good reasons to go to pg_authid instead.