Or, maybe, there is a way to do everything without changing public API.

The idea is: _wake_up_next can create a future which is set by *waked up task* on its acquiring. acquire method should wait for this future first before entering in `while self._value < 0:` loop.

If the future is cancelled, `_wake_up_next` should be called again and waiting for the next future acquiring to be performed.

If there is no *acquire waiting* future exists -- do everything as usual.

All other lock objects should be modified also.