Try to guess language by emacs major mode before file extension.

The explicit language specified in an emacs file local variable is
going to be more correct than the file extension.

highlight.scm

@@ -65,8 +65,8 @@
     ((html) 'html)
     (else #f)))
 
-(let ((type (or (guess-type-by-file-extension *file*)
+(let ((type (or (guess-type-by-emacs-major-mode-variable *file-contents*)
-                (guess-type-by-emacs-major-mode-variable *file-contents*))))
+                (guess-type-by-file-extension *file*))))
   (if (not type)
       (begin (display *file-contents*) (exit 0))
       (begin