FIBER_TASKING_LIB: Fix pthread impl of thread events
FIBER_TASKING_LIB: Fix pthread impl of thread events

These aren't actually used yet, so the API is probably going
to change

jklarowicz/FiberTaskingLib,underscorediscovery/FiberTaskingLib,jklarowicz/FiberTaskingLib,jklarowicz/FiberTaskingLib,underscorediscovery/FiberTaskingLib