Fix citext upgrade script to update derived copies of pg_type.typcollation.

Fix citext upgrade script to update derived copies of pg_type.typcollation.

If the existing citext type has not merely been created, but used in any
tables, then the upgrade script wasn't doing enough.  We have to update
attcollation for each citext table column, and indcollation for each citext
index column, as well.  Per report from Rudolf van der Leeden.