* Call self._wait() when unregistering output handlers, in order to avoid

* Call self._wait() when unregistering output handlers, in order to avoid
  triggering a tight loop. Also fix Subprocess._wait() to only schedule
  when self.registered is True.

* Add an assertion inside Scheduler._schedule_main() to try and detect tight
  loops like the one above.

* Fix typo in Scheduler._merge_exit().

svn path=/main/trunk/; revision=10989