JENA-378
The UpdateWriter needs to use a bnode to output mapping that deal with "query bnodes" in the WHERE clause.
i.e. Map ??N vars to bNode syntax on output.

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1431377 13f79535-47bb-0310-9956-ffa450edef68