simple_parallel now (partially) compiles on stable


I’ve just updated simple_parallel so that (some of) it compiles against 1.0.

Unfortunately, a lot of the API uses std::thread::scoped internally (so I’ve had to disable them), or suffers from the same unsafe problems as scoped (so I’ve had to mark it unsafe). In fact the only thing left “undamaged” is Pool::for_, but that still might be useful.

(You can get full gamut of the old functionality with the unstable feature and a nightly compiler.)