Patch to filter queues by vocabulary

I've written some code to support filtering queues by vocabulary. It works by presenting the user with a list of all available vocabularies on queue add/edit. If none are chosen, then all vocabularies are allowed in the queue. Else, only the chosen vocabularies are allowed.

Code-wise, it adds a new column to the term_queue table schema which stores a serialized array of checked vocabularies. The term_queue_add form then performs the filtering (in both the dropdown and autocomplete widgets). So, essentially, the filter is just added to the user interface.

A patch is attached against CVS tag DRUPAL-6--1-0. Please review; I've tested and it works fine on my site. Next official release will require a schema change if this is added to HEAD though.

Thanks! Nice work on this module otherwise; it was cake to modify. :)