Make `org-priority' accept an action argument `remove'

When given, the priority cookie will be removed.

lisp/ChangeLog

@@ -2,6 +2,8 @@
 
 	* org.el (org-refile): Make prefix argument 2 refile to current
 	clock.
+	(org-priority): Interpret action `remove' as call to remove the
+	priority cookie.
 
 	* org-remember.el (org-remember-apply-template): Don't depend on
 	buffer name being like file name.

lisp/org.el

@@ -10770,6 +10770,8 @@ ACTION can be `set', `up', `down', or a character."
 		have t)
 	(setq current org-default-priority))
       (cond
+       ((eq action 'remove)
+	(setq remote t new ?\ ))
        ((or (eq action 'set)
 	    (if (featurep 'xemacs) (characterp action) (integerp action)))
 	(if (not (eq action 'set))