Created the stub functions data_fetch() and data_upload() for the multi-processor API.
For details, see the message at https://mail.gna.org/public/relax-devel/2012-03/msg00011.html
(Message-id: <CAED9pY9Hb=0iywMNVBGjS=YcZgNFe+5X-nKhubKhWAWiN4Psgg@...>).
