+;; bind colon keywords for old Emacsen.
+(dont-compile
+ (condition-case nil
+ :symbol-for-testing-whether-colon-keyword-is-available-or-not
+ (void-variable
+ (let ((kwds '(:cc :date :extra :message-id :number :references :subject)))
+ (while kwds
+ (set (car kwds) (car kwds))
+ (setq kwds (cdr kwds)))))))
+