Re: [PATCH] psql: \dn+ to show size of each schema (and \dA+ for AMs)

Rebased on c727f511b.

This patch record was "closed for lack of interest", but I think what's
actually needed is committer review of which approach to take.

 - add backend functions but do not modify psql ?
 - add to psql slash-plus commnds ?
 - introduce psql double-plus commands for new options ?
 - change pre-existing psql plus commands to only show size with
   double-plus ?
 - go back to the original, two-line client-side sum() ?

Until then, the patchset is organized with those questions in mind.

--
Justin