How to walk a Lisp_String?

[Manuel Giraud]

Hi,

Some context: As discussed with Po Lu (a month or two ago), I'd like to
use some of the emacs' face machinery to render entries of Lucid menus.

I'm at a point where I'd like to walk a struct Lisp_String one
«character» at a time.  Of course, I should be able to handle multi-byte
Lisp_String.  How could I do that?

Thanks.
-- 
Manuel Giraud