Update iocp reactor to manage correctly the new _stopped flag

[therve]

Since r23345, ReactorBase now uses a new _stopped flag to correctly manage its running state. We should update the iocp reactor to use it, because it's not working correctly anymore.

The correct workflow might have been to revert the changeset, but we concluded that it could be bypassed here.

[therve]

(In [23378]) Branching to 'iocp-fix-3200'

[therve]

Please have a look.

[exarkun]

This looks pretty good.

Can you add a bit to the _SignalReactorMixin docstring? The mixin expects some methods to be implemented on the class mixing it in - eg, sigInt, sometimes sigBreak, callLater, mainLoop. It also pretty much requires that it be mixed in with ReactorBase, since it calls up to a method of that class. Maybe it would make more sense if there to be _SignalReactorBase subclassing ReactorBase and subclassed by everyone else?

[therve]

(In [23390]) Add some doc, remove some more duplication.

Refs #3200

[therve]

Okay, I updated documentation a bit. It's not awesome yet, so if you have some more idea don't hesitate. I didn't change the class hierarchy for now, because I think this is in flux so we just have to wait for something a little bit better. Please review.

[exarkun]

Looks good to me, please merge.

[therve]

(In [23392]) Merge iocp-fix-3200

Author: therve Reviewer: exarkun Fixes #3200

Fix the iocpreactor management of the new _stopped attribute introduced in r23345. It removes a fair amount of duplication between iocpreactor and posixbase in the process.