Add 'Flags: Flagged' to views sorters

After looking at the code, this is not as trivial as it sounds. There's not a flagged/unflagged column, so there would need to be some sort of SQL formula added to the orderby clause. Over my head.

// $Id$

/**
 * Handle a sort based on flagged status.
 */
class flag_handler_sort_flagged extends views_handler_sort {
  /**
   * Called to add the sort to a query.
   */
  function query() {
    $formula = $this->relationship .'.uid IS NOT NULL';
    $this->query->add_orderby(NULL, $formula, $this->options['order'], $this->table_alias . '_' . $this->field);
  }
}

This was how far I got if someone else (with more SQL knowledge than me) wants to take the ball and run with it.