Range Types

Attached is the latest version of the Range Types patch. I will get it
into better shape before the commitfest, but wanted to put up a draft in
case anyone had comments on the TODO items.

Changes:

* Uses BTree opclass rather than compare function.
* Collation specified at type definition time.
* Various fixes.

TODO:

* Should the catalog hold the opclass or the opfamily? This doesn't
affect much, but I wasn't sure which to actually store in the catalog.

* Use Robert Haas' suggestion for auto-generating constructors with
the same name as the range type, e.g. "int8range(1,10,'[]')", where the
third argument defaults to '[)'. This allows better type inference for
constructors, especially when there are multiple range types over the
same base type (and collation is a common case of this). I believe this
was the best idea after significant discussion:
http://archives.postgresql.org/pgsql-hackers/2011-06/msg02046.php
http://archives.postgresql.org/pgsql-hackers/2011-07/msg00210.php

* Send/recv functions

* cleanup

* documentation updates

Regards,
Jeff Davis