new libring XML API support

Add support the new libring data-transfer feature (DBus/wrapper).
This patch fixes only the build and doesn't add full support
for the data-transfer feature (come later),

Change-Id: If98966e28bf324260dcfc55760e11bda3e21f62b
Reviewed-by: Anthony Léonard <anthony.leonard@savoirfairelinux.com>