bug#690: 23.0.60; Function origin file misremembered

[martin rudalics]

> "C-h f prolog-mode RET" shows:
>
>    prolog-mode is a Lisp function in `prolog.el'.
>
> When I follow the link (`prolog.el'), it leads me to the wrong file,
> namely ~/emacs/lisp/progmodes/prolog.el, i.e., part of Emacs source.

Could you please try to instrument the function `find-source-lisp-file'
(in help-fns.el) for debugging before you do C-h f and tell me what it
finds?

martin