FIFO IPC support

[laserswald]

One issue I have had when trying to test Nitro is that it's damn near impossible to control an experimental window manager that's half done: it doesn't have a way to kill it from within, first of all.

To that end, I need to work on the IPC feature so I can control it via a script.

[laserswald]

The main design idea I am going for is extremely simple. Nitro will open two named pipes, one for listening and one for output. Messages on the input pipe will end in a newline, and then be split into words, turned into an ni_event, and added to the event queue.
The first word is the event name, and the rest are arguments to the event. Any events without handlers will throw an error to the output pipe, but will not crash the program. The user will need to add a handler in order to handle the message they send, but basic WM handlers are to be included by default.