mempool: better ancestor and descendant traversal.
mempool: better ancestor and descendant traversal.

decentraland/decentraland-node,VidaID/bcoin,decentraland/bronzeage-node,decentraland/decentraland-node,decentraland/decentraland-node,decentraland/bronzeage-node,VidaID/bcoin,decentraland/bronzeage-node,VidaID/bcoin