wide-edit.el for gnu emacs?

[the grue]

Hello,

some time ago, I was using the really nice "wide-edit.el" as a very
practical renaming tool. Unfortunately, it doesn't work anymore with
emacs23 or later:

http://www.emacsforum.dk/JesperPedersen/handout/wide-edit.el

When I start wide-edit-mode, I get this error:

let: Symbol's function definition is void: extent-list

It seems, extent-list is only supported by xemacs, not gnu emacs. I
have a little bit of elisp knowledge, but it is by far not enough to
fix wide-edit.el

Can someone help me with porting wide-edit to gnu emacs?
TIA,

Markus