If a role has a password expiration date, show that in psql's \du output.

If a role has a password expiration date, show that in psql's \du output.

Per a suggestion from Euler Taveira, it seems like a good idea to include
this information in \du (and \dg) output.  This costs nothing for people
who are not using the VALID UNTIL feature, while for those who are, it's
rather critical information.

Fabrízio de Royes Mello