message: don't serialize nTime for version 3 and above
diff: @@ -1231,8 +1231,10 @@ public:
  void Serialize(S &s) const {
  // Serialize nVersion
  ::Serialize(s, txTo.nVersion);
  + if (txTo.nVersion < 3) {
  // Serialize nTime
  ::Serialize(s, txTo.nTime);
  + }
  // Serialize vin
  unsigned int nInputs = fAnyoneCanPay ? 1 : txTo.vin.size();
  ::WriteCompactSize(s, nInputs);
  @@ -1327,8 +1329,10 @@ uint256 SignatureHash(const CScript& scriptCode, const T& txTo, unsigned int nIn
  CHashWriter ss(SER_GETHASH, 0);
  // Version
  ss << txTo.nVersion;
  + if (txTo.nVersion < 3) {
  // nTime
  ss << txTo.nTime;
  + }
  // Input prevouts/nSequence (none/all, depending on flags)
  ss << hashPrevouts;
  ss << hashSequence;
  