hammer_btree_search_node
n = hammer_btree_search_node(&search, node);
int hammer_btree_search_node(hammer_base_elm_t elm, hammer_node_ondisk_t node);
i = hammer_btree_search_node(&cursor->key_beg, node);
i = hammer_btree_search_node(&cursor->key_beg, node);
i = hammer_btree_search_node(&node->ondisk->elms[0].base,