message: Make GetSerialHash return const again
diff: @@ -28,7 +28,7 @@ public:
  virtual bool GetModifier(uint64_t& nStakeModifier) = 0;
  virtual bool IsZPIV() = 0;
  virtual CDataStream GetUniqueness() = 0;
  - virtual uint256 GetSerialHash() = 0;
  + virtual uint256 GetSerialHash() const = 0;
  };
  @@ -63,7 +63,7 @@ public:
  bool CreateTxOuts(CWallet* pwallet, vector<CTxOut>& vout, CAmount nTotal) override;
  bool MarkSpent(CWallet* pwallet, const uint256& txid);
  bool IsZPIV() override { return true; }
  - uint256 GetSerialHash() override { return hashSerial; }
  + uint256 GetSerialHash() const override { return hashSerial; }
  int GetChecksumHeightFromMint();
  int GetChecksumHeightFromSpend();
  uint32_t GetChecksum();
  @@ -90,7 +90,7 @@ public:
  bool CreateTxIn(CWallet* pwallet, CTxIn& txIn, uint256 hashTxOut = 0) override;
  bool CreateTxOuts(CWallet* pwallet, vector<CTxOut>& vout, CAmount nTotal) override;
  bool IsZPIV() override { return false; }
  - uint256 GetSerialHash() override { return uint256(0); }
  + uint256 GetSerialHash() const override { return uint256(0); }
  };
  