Simple XInput 2 client, for use in croutonpowerd and croutonwheel.
Make croutonpowerd use croutonxi2event:
 - No need to use xprintidle (orphan package)
 - Ping immediately on keypress (instead of having to wait up to 2 seconds)
 - Polling time can be reduced significantly
Make croutonwheel use croutonxi2event:
 - Parsing logic is simplified (output on a single line).
 - Less "garbage", croutonxi2event only outputs XInput events.
 - No hack needed to hide xinput window.