[BRLTTY] Let's improve documentation for the non blind

[Samuel Thibault]

Hello,

I'd say that what is needed is an internal representation that can
be converted both to a graphical drawing for sighted people, and a
textual description for blind people, the internal representation being
textual, so as to be modified by both sighted and non-sighted people,
patch/diff-able, etc.

This is the way xkbprint works: keys have keycode names, keyboards have
a geometric description (how keys are placed physically), and there is
a keycode -> keysym association. There could be a similar thing for
braille keyboards: basically, each driver has its set of keycode names,
each device has its geometric description of a few keys, and keytables
provide the keycode to brl_cmd mapping. Combining all of this can build
up a nice picture or textual help description.

Samuel