GdkKeymap already has support for _get_num_lock_state() and _get_caps_lock_state(). Adding _get_scroll_lock_state() would be good for completness and some backends (Windows?) could take advantage of this.
Using IsModifierKey for now
This is disabled by default. Enable with --enable-mir-backend. This backend is a combined work of Robert Ancell and Ryan Lortie.
