Implement "real" CoDel
Fix doc generation
Fix handle_join to be consistent with other handle_*'s
Make some handle_*'s type specs more precise
Call handle_out/3 on any dequeuing function

Calls handle_out on split and filter as these may result in items
being dequeued.
Restrict squeue_codel_timeout to timeout > target

If timeout =< target items would be dropped by the timeout before CoDel
could see an item above target and so CoDel would not be applied.