We had one shared parsing function for all config options so tools parse
options that don't actually make sense (e.g. --quiet or --show-keycodes for
libinput-list-devices).

This patch splits the actual libinput device configuration out and reshuffles
everything to make use of that. One large patch, because splitting this up is
more confusing than dumping it all.

This means the actual option parsing is partially duplicated between debug-gui
and debug-events but hey, not everything in life is perfect.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>