Add a special return from ccn_btree_compare to indicate a strict prefix.  Fix a bug spotted along the way.
Add a special return from ccn_btree_compare to indicate a strict prefix.  Fix a bug spotted along the way.

cawka/ndnx,cawka/ndnx,cawka/ndnx,ebollens/ccnmp,svartika/ccnx,ebollens/ccnmp,ebollens/ccnmp,ebollens/ccnmp,svartika/ccnx,svartika/ccnx,cawka/ndnx,cawka/ndnx,svartika/ccnx,svartika/ccnx,svartika/ccnx,svartika/ccnx