bug#1318: document footnote-mode

[martin rudalics]

>      \\[Footnote-renumber-footnotes]
>      \\[Footnote-goto-footnote]
>      \\[Footnote-delete-footnote]
>      \\[Footnote-cycle-style]
>      \\[Footnote-back-to-message]
>      \\[Footnote-add-footnote]
> Reorder the above with the most common operations first.

I've reordered these for Emacs 23 and fixed a couple of additional
bugs.  Please have a look, for example, via

cvs -z3 -d:pserver:anonymous@cvs.savannah.gnu.org:/cvsroot/emacs co 
emacs/lisp/mail/footnote.el

> Also
> hardwiring them here often looses track of the complete list. Perhaps
> just mention the most often used and say that is all you are mentioning.

What do you mean by "hardwiring" here?

martin