Synched head with d6 branch. Works with drush 2.x and no longer needs to be...

Synched head with d6 branch. Works with drush 2.x and no longer needs to be enabled on a site, as it is no longer a module. Hosting has not been updated to point to the right place per server, so you have to create the symlink to the central drush.php yourself. I have not sorted out the version specific stuff yet either.