pgsql-server: Some improvements for the tab-completion of psql.

Log Message:
-----------
Some improvements for the tab-completion of psql. This should
address all of the items in the todo list and adds some new
things as well. Specifically:

* Add support for ALTER SEQUENCE ...
* Add "RENAME TO" for ALTER TRIGGER xx ON yy
* Pick proper table for ALTER TRIGGER xx ON ...
* Support for ALTER USER xxx ...
* Fix ALTER GROUP xxx DROP ...
* Fix ALTER DOMAIN xxx DROP ...
* Remove "OWNER TO" from ALTER DOMAIN xx DROP ...
* Fix ALTER DOMAIN xx SET DEFAULT ..
* Prevent ALTER INDEX xxx SET TABLESPACE from using "TO"
* Support for ALTER LANGUAGE xxx (RENAME TO)
* More support for ALTER TABLE xxx ALTER COLUMN xxx ...
* More support for COPY

Greg Sabino Mullane

Modified Files:
--------------
    pgsql-server/src/bin/psql:
        tab-complete.c (r1.115 -> r1.116)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql-server/src/bin/psql/tab-complete.c.diff?r1=1.115&r2=1.116)