Fix COMMENT fontification

* lisp/org.el (org-set-font-lock-defaults): Fix regexp.

Reported-by: Martin Carlé <mc@aiguphonie.com>
<http://permalink.gmane.org/gmane.emacs.orgmode/100404>

lisp/org.el

@@ -6396,7 +6396,7 @@ needs to be inserted at a specific position in the font-lock sequence.")
 	   '(org-activate-code (1 'org-code t))
 	   ;; COMMENT
 	   (list (format
-		  "^\\*\\(?: +%s\\)?\\(?: +\\[#[A-Z0-9]\\]\\)? +\\(?9:%s\\)\\(?: \\|$\\)"
+		  "^\\*+\\(?: +%s\\)?\\(?: +\\[#[A-Z0-9]\\]\\)? +\\(?9:%s\\)\\(?: \\|$\\)"
 		  org-todo-regexp
 		  org-comment-string)
 		 '(9 'org-special-keyword t))