I know I left a note there about deadlocks but it doesn't seem to happen
anymore, especially now that the test runner creates cancellation points.
Also, what was this `can_set_thread_cancel_state` for? It does not make
sense to me that it enables cancellation, and then does it again later.
With the comment it seems like it should be `.DISABLE` to first disable
and then wait for the thread to start. But even that seems weird, why
do you need to do that? I removed it.
71afb8e7a5