suppress byte-compiler warning about unprefixed global variables from calendar.el

* lisp/org.el: add with-no-warning to defvar for two unprefixed global
  variables from calendar.el (there's nothing else we can do inside
  org until it is fixed in calendar.el).

lisp/org.el

@@ -4891,9 +4891,9 @@ This is for getting out of special buffers like remember.")
 
 ;; FIXME: Occasionally check by commenting these, to make sure
 ;;        no other functions uses these, forgetting to let-bind them.
-(defvar entry)
+(with-no-warnings (defvar entry)) ;; unprefixed, from calendar.el
 (defvar org-last-state)
-(defvar date)
+(with-no-warnings (defvar date)) ;; unprefixed, from calendar.el
 
 ;; Defined somewhere in this file, but used before definition.
 (defvar org-entities)     ;; defined in org-entities.el