SHOW FUNCTIONS should return the functions sorted by signature.

Change-Id: Ia843331ff22bd482e716ed12e09b6778fc53dac2
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2804
Reviewed-by: Marcel Kornacker <marcel@cloudera.com>
Reviewed-by: Skye Wanderman-Milne <skye@cloudera.com>
Tested-by: jenkins