org-clock.el: require 'org-exp to set `org-export-default-language'.

Thanks to Matt Lundin for reporting this.

lisp/org-clock.el

@@ -29,6 +29,7 @@
 ;; This file contains the time clocking code for Org-mode
 
 (require 'org)
+(require 'org-exp)
 ;;; Code:
 
 (eval-when-compile