message: Reject version 4 spends before they are active.
diff: @@ -4042,6 +4042,8 @@ bool ContextualCheckZerocoinSpend(const CTransaction& tx, const libzerocoin::Coi
  const CBigNum& bnPubcoin = spend.getPubcoinValue();
  if ((!fVerifying && !fReindex) && !IsPubcoinInBlockchain(GetPubCoinHash(bnPubcoin), nHeightTx, txid, pindex->pprev))
  return error("%s: pubcoinhash %s is not found in the blockchain", __func__, GetPubCoinHash(bnPubcoin).GetHex());
  + } else if (spend.getVersion() == libzerocoin::CoinSpend::V4_LIMP) {
  + return error("%s: zerocoinspend v4 while v4 is not active", __func__);
  }
  libzerocoin::SpendType expectedType = libzerocoin::SpendType::SPEND;
  