Hard reboot with pending threads will crash Dream Daemon

Possible outcomes:

* Thread is not `join()`ed - `~thread` calls `terminate()` calls `abort()`
* Thread is `join()`ed during global destructor - indefinite hang
* Thread is `detach()`ed - crash when thread tries to access now-unloaded code or memory

Test case here: https://gist.github.com/SpaceManiac/b23ec263e786c09dc89f0399b97e71fc