- Patch #12232 by Steven: more search improvements:

   + When a comment is posted, a node needs to be re-indexed. Luckily, we can use node_comment_statistics for this easily.
   + When a node is deleted, it should be deleted from the search index as well.
   + The search wipe didn't properly remove links to nodes from the index.
   + Section url was faulty in _help.
   + Minor code rearrangement.