ob-R: Allow more :results values

* lisp/ob-R.el (org-babel-header-args:R): Allow "drawer" and "none",
  since they are supported in `org-babel-common-header-args-w-values'.

Reported-by: Andreas Leha <andreas.leha@med.uni-goettingen.de>
<http://permalink.gmane.org/gmane.emacs.orgmode/97683>

lisp/ob-R.el

@@ -63,8 +63,8 @@
     (useDingbats	 . :any)
     (horizontal		 . :any)
     (results             . ((file list vector table scalar verbatim)
-			    (raw org html latex code pp wrap)
-			    (replace silent append prepend)
+			    (raw html latex org code pp drawer)
+			    (replace silent none append prepend)
 			    (output value graphics))))
   "R-specific header arguments.")