psql tab-complete and backslash patch

Hi!

attached is a patch against psql that makes psql's tabcomplete code
ROLES aware, adds SET SCHEMA and basic CREATE DATABASE/TRIGGER support
as well as some other minor things.
In addition to this I modified \du to display a list of roles with some
additional information(createrole,connection limit) on 8.1 with a
fallback to the original output on older backends.

There are a few problems still left - in particular the the tab-complete
code is a little inconsistent wrt completing USER/ROLE/GROUP/OWNER TO
with roles or users/groups (from the pg_user/pg_group views)

comments(especially about the \du change)?

regards

Stefan Kaltenbrunner

Changes in Detail:

*) SET SCHEMA for ALTER AGGREGATE,FUNCTION.DOMAIN,SEQUENCE,TABLE,TYPE
*) add CONNECTION LIMIT to ALTER DATABASE
*) add support for ALTER ROLE
*) make ALTER USER aware about ROLES
*) COMMENT ON LARGE OBJECT
*) add support for CREATE DATABASE
*) add support for CREATE TRIGGER
*) add support for CREATE USER,ROLE,GROUP
*) complete SET ROLE with a list of roles
*) complete SET SCHEMA with a list of schemas
*) complete SET SESSION AUTHORIZATION with list of roles
*) fixes a small typo in a comment (ANALZYE -> ANALYZE)
*) modify \du to display createrole and the connection limit