[PATCH] psql: add size-based sorting options (O/o) for tables and indexes

Hello,
This patch adds two new meta-command modifiers for \dt(+) and \di(+):

  - O  : sort by total relation size descending
  - o  : sort by total relation size ascending

This makes it easier to identify the largest tables and indexes
without writing custom SQL queries.

Help message (\?) is updated to reflect the new options.

regards,
-- 
M.Atıf Ceylan