Re: autoconf-mode fontification

["Björn Bidar" <bjorn.bidar@thaodan.de>]

Ah I got what was different.

With Emacs -Q I was using the builtin autoconf mode while currently I'm
using the autoconf-mode.el from the autoconf package.

Once I switched over that mode to also use derived-mode and be closer to
what m4-mode does even that one worked again:

;;;###autoload
(define-derived-mode autoconf-mode prog-mode "ac"
  "A major-mode to edit Autoconf files like configure.ac.
\\{autoconf-mode-map}
"
  :syntax-table autoconf-mode-syntax-table
  (setq-local add-log-current-defun-function #'autoconf-current-defun)
  (setq-local comment-start "# ")
  (setq-local parse-sexp-ignore-comments t)
  (setq-local font-lock-defaults '(autoconf-font-lock-keywords nil)))