Add support for LED_COMPOSE and LED_KANA USB HID LEDs
Requires xkbcommon 1.8.0, which is unreleased at the time of this commit. Libinput 1.26 already is.
See libinput/libinput!990 (merged) for more info.
I have also thrown out some now-useless ifdefs from 8 years ago that were relying on a specific xkbcommon version, which is now guaranteed.