/** Add or delete a (key,value) pair from a bi-hash table
@param h - the bi-hash table to search
- @param add_kv - the (key,value) pair to add
+ @param add_v - the (key,value) pair to add
@param is_add - add=1, delete=0
@returns 0 on success, < 0 on error
@note This function will replace an existing (key,value) pair if the