(add-to-list 'auto-mode-alist
'("/ac\\(include\\|local\\)\\.m4\\'" . autoconf-mode))
+;; Default for XSL and XML files.
+(add-to-list 'auto-mode-alist '("\\.xsl$" . sgml-mode))
+(add-to-list 'auto-mode-alist '("\\.xml$" . sgml-mode))
+
;; When an Emacs init file gets large or has a lot of function definitions, you
;; should consider compiling it: it will load faster when Emacs starts, and its
;; functions will execute faster.