(pp-to-string): Don't use emacs-lisp-mode.

Just do the parts of it we actually want.

lisp/emacs-lisp/pp.el

@@ -32,7 +32,8 @@ that `read' can handle, whenever this is possible."
     (set-buffer (generate-new-buffer " pp-to-string"))
     (unwind-protect
 	(progn
-	  (emacs-lisp-mode)
+	  (lisp-mode-variables)
+	  (set-syntax-table emacs-lisp-mode-syntax-table)
 	  (let ((print-escape-newlines pp-escape-newlines))
 	    (prin1 object (current-buffer)))
 	  (goto-char (point-min))