Correct the documentation on the return value of ccn_btree_insert_content.
Correct the documentation on the return value of ccn_btree_insert_content.

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