RUSTSEC-2020-0061 futures_task::noop_waker_ref can segfault due to dereferencing a NULL pointer

Affected versions of the crate used a UnsafeCell in thread-local storage to return a noop waker reference, assuming that the reference would never be returned from another thread. This resulted in a segmentation fault crash if Waker::wakebyref was called on a waker returned from another thread du...