This commit adds an output struct which abstracts the X11 specific
functions and makes it possible to easily create a drop-in wayland
output.
It also fixes a bug in wayland where notifications won't disappear.
This is because wayland doesn't give access to user input when a
client is not in focus. This way it seems like the user is always
idle. The idle functionality is now disabled in Wayland until proper
support is added.
