Patch by Marco:

- forum: fixed link to new topic
- forum: new topic shows default forum correctly
- forum: first_new is back; the anchor didn't consider multiple pages
- forum: use standard pager, needed some changes/fixes to pager.inc
- forum: some cleanup
- forum: taxonomy hook
- renamed first_new to simply new
- added an optional parameter to pager_query for the count query
- used the optional count param for paging forum topics
- internal change: moving a topic doesn't duplicate the node anymore but just
  changes the forum (term); no change in functionality, and shadow still
  works (suggested by Dries).  This probably also made some queries somewhat
  lighter.
- bug fixed: anonymous users always saw "n (n new)" in the replies column
- updated pager help and moved from _help to phpdoc