use libxkbcommon-x11 instead of libX11
little cleanups thanks to Ran Benita’s review
listen for XKB events instead of the MappingNotify event (Thanks Ran)
remove obsolete xkb_state_update_key() calls (Thanks Ran)
Merge remote-tracking branch 'origin/master'

Conflicts:
	Makefile
	i3lock.c

X11 dependencies were eliminated from i3lock, but i3lock-blur still
needs them because of glX.