message: Simplify the code to only rely on op_spend checking
diff: @@ -2729,16 +2729,7 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
  if(!nonZeroVersion){
  //if tx is 0 version, then the tx must already have been added by a previous contract execution
  - bool found=false;
  - //iterate backwards because the AAL tx should have been added by the last contract exec, though there can be multiple txs by a single contract tx
  - for (unsigned int j = checkBlock.vtx.size()-1; j > 0; j--)
  - {
  - const CTransaction &ctx = *(checkBlock.vtx[j]);
  - if(ctx.GetHash() == tx.GetHash()){
  - found = true;
  - }
  - }
  - if(!found){
  + if(!tx.HasOpSpend()){
  return state.DoS(100, error("ConnectBlock(): Version 0 contract executions are not allowed unless created by the AAL "), REJECT_INVALID, "bad-tx-improper-version-0");
  }
  }
  