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, and epoll interfaces are provided.

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

Changes:

* add TimerFD::CANCEL_ON_SET constant
ref: http://www.man7.org/tlpi/api_changes/
* fix concurrent Epoll#wait on the same epoll fd
* SignalFD interface removed (unworkable with Ruby runtimes)
* use rb_update_max_fd() if available (Ruby 1.9.3)
* reintroduce SLEEPY_PENGUIN_VERSION constant ("3.1.0")