idle-notify: new protocol
This patch adds a new idle-notify protocol. It allows clients to be notified when the user is idle. Use-cases include messaging applications marking the user as away and clients saving resources when there's no activity.
This protocol is based on the org_kde_kwin_idle interface already being used by KDE and wlroots compositors. The protocol has been sent to wayland-protocols in 2015 1. This version renames and clarifies the interfaces, and addresses the review comments.
- Consider making the seat argument null-able, to target all seats
- Consider adding an optional output argument for e.g. DPMS (how to tie that with input though?)
- Consider specifying that a zero timeout is valid