I attached a patch with a more complete test of kqueue. It's not that
great, but it's a thing. I've only tested on OS X, but it works.

Regarding the ability of building an epoll object from a fd, it might be
usefull in some corner cases, but that's not a priority.

exarkun looked at the patch and told me that there may be some
threadsafety issues: for example, when calling epoll_wait, you use
self->evs unprotected. It's not very important, but you may want to tell
it in the documentation.

As you started the rich comparison for kevent objects, it may be
interesting to have full comparison (to sort list of events). It's not a
high priority though.

That's all for now!