message: Completely disallow overwrite
diff: @@ -88,7 +88,7 @@ void AddCoins(CCoinsViewCache& cache, const CTransaction &tx, int nHeight) {
  for (size_t i = 0; i < tx.vout.size(); ++i) {
  // Pass fCoinbase as the possible_overwrite flag to AddCoin, in order to correctly
  // deal with the pre-BIP30 occurrances of duplicate coinbase transactions.
  - cache.AddCoin(COutPoint(txid, i), Coin(tx.vout[i], nHeight, fCoinbase, fCoinstake), fCoinbase || fCoinstake);
  + cache.AddCoin(COutPoint(txid, i), Coin(tx.vout[i], nHeight, fCoinbase, fCoinstake), false);
  }
  }
  