sleepy_penguin provides access to newer, Linux-only system calls to wait
on events from traditionally non-I/O sources. Bindings to the eventfd,
timerfd, inotify, signalfd and epoll interfaces are provided.

* http://bogomips.org/sleepy_penguin/
* sleepy.penguin@librelist.com />* git://bogomips.org/sleepy_penguin.git

Changes:

One bugfix:

* epoll: avoid race condition in EINTR checking

Even if we timeout while getting an EINTR, we'll retry
epoll_wait() with a zero timeout like IO.select does in Ruby to
avoid raising Errno::EINTR.