@param h - the bi-hash table to search
@param add_v - the (key,value) pair to add
- @param is_add - add=1, delete=0
+ @param is_add - add=1 (BIHASH_ADD), delete=0 (BIHASH_DEL)
@returns 0 on success, < 0 on error
@note This function will replace an existing (key,value) pair if the
new key matches an existing key