Fix compiler warnings.

Thanks to Achim Gratz for reporting these problems.

lisp/org-macro.el

@@ -42,7 +42,9 @@
 (declare-function org-element-context "org-element" (&optional element))
 (declare-function org-element-property "org-element" (property element))
 (declare-function org-element-type "org-element" (element))
-
+(declare-function org-remove-double-quotes "org" (s))
+(declare-function org-file-contents "org" (file &optional noerror))
+(declare-function org-with-wide-buffer "org-macs" (&rest body))
 
 ;;; Variables
 

lisp/org.el

@@ -14661,7 +14661,8 @@ value for the property."
   (interactive)
   (org-set-effort nil t))
 
-(defvar org-clock-effort "") ;; Defined in org-clock.el
+(defvar org-clock-effort)       ;; Defined in org-clock.el
+(defvar org-clock-current-task) ;; Defined in org-clock.el
 (defun org-set-effort (&optional value increment)
   "Set the effort property of the current entry.
 With numerical prefix arg, use the nth allowed value, 0 stands for the