Events: Scheduler / Epoll: set read and write file descriptors

This patchs makes the Events channel creation to use two file descriptors
for read and write operations. Mostly because kqueue based interface
will use old-fashion pipe(2) as eventfd() is not available.

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
Events: kqueue: implement channels_create() handler

Signed-off-by: Eduardo Silva <eduardo@monkey.io>