* fix issue32208: update threading.Semaphore docs and add unit test to validate correct behavior

* add test for blocking

* Update threading.rst

* semaphore: remove documentation validation tests and move 'return value' test to BaseSemaphore

Original patch by James Edwards.

Patch from Mattip.

Related Issues:

#issue21528
#issue24453

Patch by Denver Coneybeare with some test modifications by me.

It is unfortunate that the '_' names were not kept as aliases, and that RLock
was not also converted to a class, but it is now too late to change either of
those things for 3.3.

return False when the event was set and cleared right after.