baroque french tab support

[contact]

Hi all !

As Mike asked us some work for his long travel accross the seas, I've
asked him to automate some tricks to obtain accurate french tabs (for
the viol and lute especially). Here are the requirements :

- letters instead of figures (already done)
- upper string on top (already done)
- letters above the dedicated line and under the next line
- after letter "i" is letter "k" (no "j")
- the ancient "r" used instead of "c" (because of confusion with
letter "e") can be abandonned because engraving is now ok
- rythms are indicated above the staff just once as long as it remains
the same (a new indication occurs when value changes).Rythm indication
is mandatory for the first note after each barline. As barlines are not
linked to time signature, it would be usefull to have a command that
forces rythm indication (just like forcing accidental with !)
- letters with descenders have to be adapted ("b", "d", "h", ...)
as it can be seen here :
http://imslp.org/wiki/Special:ImagefromIndex/73285 (HUME) and there :
http://imslp.org/wiki/Special:ImagefromIndex/98846 (Corkine). I think
these two examples show the same alphabet which could be fairly used for
this support.

Best regards.