bug#417: dired-guess-shell-alist-user examples enhancement

[jidanni]

In Info (dired-x)Shell Command Guessing, at
`dired-guess-shell-alist-user' and also in its docstring, please add:

Q: I don't like that dired-guess-shell-alist-default uses "xloadimage"
and "display". I want to use "xli". What can I do?

A:
(setq dired-guess-shell-alist-user
  (list
    (list "\\.png$" "xli")
    (list "\\.gif$" "xli")...;;they already have such examples, but not:
;;or
    (list "\\.\\(jpe?g\\|png\\|p[bgpn]m\\|gif\\)$" "xli");;researched 1 hour
;;or
some fancy car cad thing that changes all xloadimage and display;;(please add)
;;or use symlinks in ~/bin ;; yuck

Also in Info mention dired-guess-shell-case-fold-search.

P.S. The popular ".mp3" format needs a default command. mplayer?