Split Poll into Poll and Register

[carllerche]

This also makes Poll::poll require &mut self since Poll is no
longer expected to be stored in a Sync context.

Resolves #757

This is a very large change and I would not look for perfection, just that nothing in the change is terribly broken. This will be but one of many PRs to transition Mio to 0.7 and I am attempting to make it as incremental as possible.

cc @Thomasdezeeuw @stjepang

[Thomasdezeeuw]

Mostly looks good to me, added some small comments.

The only thing I don't really like is poll.register().register(...) in some of the tests. Maybe get_register or register_ref would make it better.

[carllerche]

@Thomasdezeeuw I agree with you about the tests and poll.register().register(...). However, I hope to punt that until later.

• Many tests will be deleted (as we delete old functionality).
• Tests need a general overhaul. I think this would be best done after the Mio API changes are done.
• I am not sure exactly sure what the best strategy will be for us. We may just want to bring back Poll::register, reregister, deregister and rename register() -> handle() or something. I think we can better evaluate that after the changes we know we want are done.

Thoughts?

[seanmonstar]

The only thing I don't really like is poll.register().register(...)

I agree that the stuttering feels weird. What if the type Register were renamed to Registry? Then it reads as poll.registry().register(..)...

[carllerche]

@seanmonstar @Thomasdezeeuw I don't have a huge opinion re: what Register should be called. If we want to change to Registry, we can do that.

[hawkw]

FWIW, I'm +1 on renaming Register to Registry

[ghost]

Same here. Even though Register can be a noun, it sounds more like an action to me, while Registry would be unambiguous.

[Thomasdezeeuw]

Registry is fine by me.

[Thomasdezeeuw]

LGTM