ispell, iso-8859-15, and emacs together

[Le TeXnicien de Surface]

Hello

I'm using emacs 21.3.1 on a Suse 10.1 for x86_64.

I've changed a french dictionary used by ispell to enable the checking of
iso-8859-15 (latin 9) coded text and it works alone (command line).

I would like to add the necessary tips to my emacs file to enable Emacs to
use that dictionary with ispell [I've tried aspell but I've got some other
mess I'll perhaps adress some other day :( ]

With SuSe comes a ispell-emacs-menu.el which uses some language scripts such
as this one

<script>
;; Used by ispell-emacs-menu.el
;; Do *not* byte-compile this file because its loaded by both emacs and
xemacs

(append-ispell-dict-alist       "francais.hash"
   '("francais-tex"
      "[A-Za-z'\"\\`^}{]"
     "[^A-Za-z'\"\\`^}{]"
     "[---'\"\\`^}{]" t ("-d" "francais") "~tex" nil))

(append-ispell-dict-alist       "francais.hash"
   '("francais"
     
"[A-Za-z\300\302\307\310-\313\316\317\324\331\333\334\340\342\347\350-\353\356\357\364\371\373\374]"
    
"[^A-Za-z\300\302\307\310-\313\316\317\324\331\333\334\340\342\347\350-\353\356\357\364\371\373\374]"
     "[---']" t ("-d" "francais") "~list" iso-latin-1))
</script>

I failed to understand what the \300 and the like represent. 

I think to have understood that I must declare the characters considered as
letters and, for iso-8859-15 to be useful, I need œ (&oelig;), Œ, æ and Æ.

Any hint heartily wellcome.

-- 
Le TeXnicien de Surface