dequeue_towards: always return active tasks; join_work: imitate worker more closely, keep active if queue appears to be blocked for the moment -- it may become free again after some worker_finished event;

merged

removed unused low-level interrupts;

tuned signature;

tuned;

more specific conditions: scheduler_event, work_available, work_finished -- considereably reduces overhead with many threads; more specific signal vs. broadcast; execute/finish: more careful notification based on minimal/maximal status; tuned shutdown;

enqueue/finish: return minimal/maximal state of this task;