ob-J: allow also letter 'j' indicate J code

* lisp/ob-J.el (org-babel-execute:j): Make `org-babel-execute:j' an
  alias of `org-babel-execute:J'.  This allows to use the letter
  'j' (and not only 'J') to identify the J-language for a source-block.

  Note: The source-block marked with 'j' gets the highlighting
  according j-mode.

lisp/ob-J.el

@@ -66,6 +66,8 @@ PROCESSED-PARAMS isn't used yet."
 	 (org-babel-J-interleave-echos-except-functions s3)))
     (org-babel-J-interleave-echos body)))
 
+(defalias 'org-babel-execute:j 'org-babel-execute:J)
+
 (defun org-babel-execute:J (body params)
   "Execute a block of J code BODY.
 PARAMS are given by org-babel.