ODBC and Kerberos

Finally got around to testing the new ODBC version for Kerberos support, and I'm happy to report it works perfectly and requires no hacks to install.

To use it, make sure you have a libpq with Kerberos support compiled in (yeah, this means manual build - we're looking into this for 8.1, but no promises yet). Then just set up your data source as you normally would, and skip specifying the password (you must specify a username though). As long as your pg_hba.conf is properly set up, that's all you need.