[kbd] I: kbd + xkb

Hi!

I implemented initial proof of concept[1] for using layouts from XKB.
Using xkbcommon I process loadkeys arguments and convert the resulting
configuration into a kernel keymap. Only what is supported by the kernel
is converted.

This support does not replace regular keymaps. There are no plans for
this.

The command looks like:

loadkeys --xkb-layout="us,ru,fr" --xkb-options="grp:caps_toggle"

This implementation is inspired by the console-setup[2] project. Many
thanks to Anton Zinoviev for help.

At the moment compose is not implemented. This is because xkbcommon does
not provide an API for iterating over a compose table. I hope to solve
this problem in the future.

If you're interested then comments, bug reports and patches are welcome!

[1] https://github.com/legionus/kbd/tree/xkbcommon
[2] https://salsa.debian.org/installer-team/console-setup.git

-- 
Rgrds, legion