Remove create temporary tables from comment.install

Once the search patch is in, this will be the last remaining use of CREATE TEMPORARY TABLES in core. Starting this issue to look at alternatives to the query to see if we could remove it for D6.

comment_enable

/**
 * Implementation of hook_enable().
 */
function comment_enable() {
  // Insert records into the node_comment_statistics for nodes that are missing.
  db_query_temporary("SELECT n.nid, n.changed, n.uid FROM {node} n LEFT JOIN {node_comment_statistics} c ON n.nid = c.nid WHERE c.comment_count IS NULL", 'missing_nids');
  db_query("INSERT INTO {node_comment_statistics} (nid, last_comment_timestamp, last_comment_name, last_comment_uid, comment_count) SELECT n.nid, n.changed, NULL, n.uid, 0 FROM missing_nids n");
}