Fixed threadpool hang and added lots of smoketests.
* Fixed bug in threadpool logic when calling CleanupAnyWorkersSharingAllocator - this was deleting the worker's thread death notifier in the context of a worker thread (which is only allowed from the context of the main thread).
* Added lots more smoketests
* Added --overwrite option to fzip (previously unzipping would always overwrite)
---------------------------- Test N1 ------------------------------
1:abc
2:def
---------------------------- Test N2 ------------------------------
1:abc
def
2:ghi
jkl---------------------------- Test N3 ------------------------------
2:def
3:
ghi
jkl---------------------------- Test N4 ------------------------------
2:ghi
jkl---------------------------- Test N5 ------------------------------
1:abc
2:def
3:ghi
4:jkl---------------------------- Test N6 ------------------------------
1:abc
2:def
3:ghi
4:jkl