I can't remember who said they were working on schema related psql

I can't remember who said they were working on schema related psql
changes, but I kept finding myself wishing I could see what schema a
table or view exists in when I use \dt, \dv, etc. So, here is a patch
which does just that.

It sorts on "Schema" first, and "Name" second.

It also changes the test for system objects to key off the namespace
name starting with 'pg_' instead of the object name.

Sample output:

test=# create schema testschema;
CREATE SCHEMA
test=# create view testschema.ts_view as select 1;
CREATE VIEW
test=# \dv
                  List of relations
         Name        |   Schema   | Type |  Owner
--------------------+------------+------+----------
  __testpassbyval    | public     | view | postgres
  fooview            | public     | view | postgres
  master_pg_proc     | public     | view | postgres
  rmt_pg_proc        | public     | view | postgres
  vw_dblink_get_pkey | public     | view | postgres
  vw_dblink_replace  | public     | view | postgres
  ts_view            | testschema | view | postgres
(7 rows)

Joe Conway