and its event queue is empty.
The DONEOK flag is forced to true if there are no references to a task,
its event queue is empty, and it is shutting down.
Add isc_task_unsend() and isc_task_unsendrange().
Add isc_task_sendanddetach().
Event tags are now void *.
Code cleanups.
Various shutdown bug fixes.
Make tracing messages prettier.