Documentation: Using Emacs-mode

[Heikki Johannes Junes]

The part of documentation which deals how to install Emacs-mode for
LilyPond could be shorter and more informative for an user. The following
is needed to install it as a user:

Add "~/site-lisp" to load-path with the following line in ~/.emacs:

(setq load-path (append (list (expand-file-name "~/site-lisp")) load-path))

Copy lilypond-mode.el, lilypond-font-lock.el and lilypond-indent.el to
~/site-lisp/ and lilypond-init.el to ~/site-lisp/site-init.d/.

That is much shorter and not just "somewhere in load-path". An user may
need precise advice.

      Heikki Junes