R batch files: update code repository

git-svn-id: https://svn.osgeo.org/grass/grass/branches/releasebranch_7_0@70072 15284696-431f-4ddb-bdfa-cd5b030d7da7

mswindows/external/README.license

@@ -17,5 +17,5 @@ comments carefully.
 
  * Windows batchfiles for use with R / (GNU GPL v2)
    http://code.google.com/p/batchfiles/
-
+   https://github.com/ggrothendieck/batchfiles (new code repository)