PostgreSQL harness support on client side

Hi there,

As part of getting DamZ's Puppet testbot stuff working for a Postgres environment, we need to get the Postgres driver for PIFR client working properly.

The main issue is that D6 can't load two database drivers at the same time, so we have to use a PDO connection to hook into the Postgres database, rather than just using db_set_active(). On top of that, we need to open a second connection to Postgres that's not in the context of the checkout DB in order to drop/create the DB, as Postgres doesn't let you drop a database while it's active.

I've crafted a patch for PIFR 2.2, which the Puppet Drush-make uses, which I'm attaching here so I can reference it in the testbot Drush-make file.

I'll also attach my WIP patch against 2.x-dev, which works as far as getting the database up and running, but it seems the current snapshot isn't working properly (D7 installer fails, documented in #972956: Update Drupal 7 installer to reflect installer form changes, and once that's patched, the quick self-test appears to do a full test...).

There's probably also work that needs to go into the server side to support farming out tests to pgsql bots, but I'm not really across what needs to happen there. Hit me (neilnz) or fiasco up on #drupal-contribute if you want to chat about that.

Patches follow. Note the 2.2 patch is quite old now, fiasco actually created it several months ago, but it's essentially the same as the 2.x one I rolled just now.