Add the 'changed' field to the $topics variable

I'm using the forums module in a sligthly specific way, which requires the use of the 'changed' field from the node db-table.
In order to do this today, I need to hack the forum.module to add the the field to the sql query.

I suggest adding the 'changed' field to the $topics variable in core, because that way, it is themeable.

As far as I can tell, there is only one place that needs a change:

In forum.module:

function forum_get_topics

• line 582: the $sql variable: add n.changed to the list of fields to select. (see the following example, including the n.changed AS last_changed addition)
• $sql = db_rewrite_sql("SELECT n.nid, r.tid, n.title, n.type, n.sticky, u.name, u.uid, n.created AS timestamp, n.changed AS last_changed, n.comment AS comment_mode, l.last_comment_timestamp, IF(l.last_comment_uid != 0, cu.name, l.last_comment_name) AS last_comment_name, l.last_comment_uid, l.comment_count AS num_comments, f.tid AS forum_tid FROM {node_comment_statistics} l INNER JOIN {node} n ON n.nid = l.nid INNER JOIN {users} cu ON l.last_comment_uid = cu.uid INNER JOIN {term_node} r ON n.vid = r.vid INNER JOIN {users} u ON n.uid = u.uid INNER JOIN {forum} f ON n.vid = f.vid WHERE n.status = 1 AND r.tid = %d");

Alas, I don't know how to create a patch, otherwise I would.