These are only used inside xkb/*, so no need to keep them exported.
Also replacing some macros by inline functions in order to improve
type-safety and debugging, and adding documentation.
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1729>
