When ccn_get needs to use a chuld handle, borrow the parent's key cache.
When ccn_get needs to use a chuld handle, borrow the parent's key cache.

refs #316  Implementation of versioning in c lib

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