PostgreSQL fix

In addition to this old bug there is another bug in cvs version of forum.module, when the database in use is PostgreSQL. When forum configuration page is accessed first time, Drupal attempts to create a new vocabulary for forums:

INSERT INTO vocabulary (name, description, help, multiple, required, hierarchy, relations, tags, weight, module, vid) VALUES ('Forums', '', '', 0, 1, 1, 0, '', 0, 'forum', '1')

Unfortunately, this throws an 'Invalid input syntax for integer' error, as no value is assigned for field 'tags'.

I've included a patch that should insert 0 into that field to avoid the error, but I hope someone would review it, as I'm no expert in PHP and thus unsure that I made it correctly. Only one row is affected.