It's common enough for users to want to debug libinput behavior without
interference by the compositor or the X server. Being able to run a GUI
without having to compile from git is helpful.
Note that this changes --enable-event-gui autotools option to
--enable-debug-gui and the event-gui mesonconf option to debug-gui.
This also drops the standalone event-gui binary in both autotools and meson.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
