* XKB-Config(7), XKB-Enhancing(7): user-level documentation
for XKB configuration; not perfect, but the best available.
* xtrans(3): a library actively maintained upstream.
* libXmu and libXext: Many libraries are effectively frozen upstream.
According to matthieu@, the documentation of libXmu and libXext
is among the most valuable of those.
Feedback and OK matthieu@.
