Attached is a new version of a patch to add a CITEXT contrib module.
Changes since v2:
* Optimized citext_eq() and citext_ne() (the = and <> operators,
respectively) by having them use strncmp() instead of varstr_cmp().
Per discussion.
* Added `RESTRICT` and `JOIN` clauses to the comparison operators (=,
<>, <, >, <=, >=). These improve statistics estimations, increasing
the liklihood that indices will be used.
Thanks!
David
