message: Regtest: mine the correct version blocks
  Zerocoin rules mandate that block version must be < 4 prior to zerocoin
  activation height. To prevent erroring on regtest, and still allow for
  manual/scripted changing of the block version, set some locical defaults
  .
diff: @@ -114,8 +114,14 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn, CWallet* pwallet,
  // -regtest only: allow overriding block.nVersion with
  // -blockversion=N to test forking scenarios
  - if (Params().MineBlocksOnDemand())
  + if (Params().MineBlocksOnDemand()) {
  + if (fZerocoinActive)
  + pblock->nVersion = 5;
  + else
  + pblock->nVersion = 3;
  +
  pblock->nVersion = GetArg("-blockversion", pblock->nVersion);
  + }
  // Create coinbase tx
  CMutableTransaction txNew;
  