in order to have the same resolution as pthreads condition variables.
At the same time, it must be large enough to accept 31 bits of
milliseconds, which is the maximum timeout value in the windows API.
A PY_LONG_LONG of microseconds fullfills both requirements.
This closes issue #20737
Fix incorrect test of the condition variable state, spotted by
Richard Oudkerk. This could cause the internal condition variable
to grow without bounds.
