message: Compute the stake modifier every new block
diff: @@ -3157,6 +3157,7 @@ CBlockIndex* AddToBlockIndex(const CBlockHeader& block)
  }
  pindexNew->nTimeMax = (pindexNew->pprev ? std::max(pindexNew->pprev->nTimeMax, pindexNew->nTime) : pindexNew->nTime);
  pindexNew->nChainWork = (pindexNew->pprev ? pindexNew->pprev->nChainWork : 0) + GetBlockProof(*pindexNew);
  + pindexNew->nStakeModifier = ComputeStakeModifier(pindexNew->pprev, block.IsProofOfWork() ? hash : block.PrevoutStake().hash);
  pindexNew->RaiseValidity(BLOCK_VALID_TREE);
  if (pindexBestHeader == NULL || pindexBestHeader->nChainWork < pindexNew->nChainWork)
  pindexBestHeader = pindexNew;
  