ob-R: make it work with older ESS versions

* lisp/ob-R.el (org-babel-R-initiate-session): The PROC argument is
  mandatory for older ESS versions.

lisp/ob-R.el

@@ -36,7 +36,7 @@
 (declare-function ess-make-buffer-current "ext:ess-inf" ())
 (declare-function ess-eval-buffer "ext:ess-inf" (vis))
 (declare-function ess-wait-for-process "ext:ess-inf"
-		  (&optional proc sec-prompt wait force-redisplay))
+		  (proc &optional sec-prompt wait force-redisplay))
 (declare-function org-number-sequence "org-compat" (from &optional to inc))
 (declare-function org-remove-if-not "org" (predicate seq))
 (declare-function org-every "org" (pred seq))
@@ -264,7 +264,9 @@ This function is called by `org-babel-execute-src-block'."
 	    ;; Session buffer exists, but with dead process
 	    (set-buffer session))
 	  (require 'ess) (R)
-	  (ess-wait-for-process)
+	  (ess-wait-for-process
+	   (get-process (or ess-local-process-name
+			    ess-current-process-name)))
 	  (rename-buffer
 	   (if (bufferp session)
 	       (buffer-name session)