Fix protobuf-mode on XEmacs.

editors/protobuf-mode.el

diff --git a/editors/protobuf-mode.el b/editors/protobuf-mode.el
index 3337c1f..9ac0c72 100644
--- a/editors/protobuf-mode.el
+++ b/editors/protobuf-mode.el
@@ -206,7 +206,8 @@
         abbrev-mode t)
   (use-local-map protobuf-mode-map)
   (c-initialize-cc-mode t)
-  (c-make-emacs-variables-local)
+  (if (fboundp 'c-make-emacs-variables-local)
+      (c-make-emacs-variables-local))
   (c-init-language-vars protobuf-mode)
   (c-common-init 'protobuf-mode)
   (easy-menu-add protobuf-menu)