(icon-mode-map): Added menus.

(icon-mode-map): Added menus.
(icon-imenu-generic-expression): New variable to be used for imenu.
(icon-mode): Added font-lock, imenu and hideshow support.
(icon-font-lock-keywords-1, icon-font-lock-keywords-2):
New constants for different level of font-lock fontification.
(icon-font-lock-keywords): New variable.  Default expression to be
assigned to font-lock-keywords in `icon-mode'.
(icon-forward-sexp-function): New function used as `forward-sexp' by hideshow.