message: arith: fix some constructor issues.
diff: @@ -281,7 +281,7 @@ public:
  {
  unsigned int nSize = BN_bn2mpi(bn, NULL);
  if (nSize < 4)
  - return 0;
  + return uint256(0);
  if (bitSize() > 256) {
  return MaxUint256();
  }
  @@ -289,7 +289,7 @@ public:
  BN_bn2mpi(bn, &vch[0]);
  if (vch.size() > 4)
  vch[4] &= 0x7f;
  - uint256 n = 0;
  + uint256 n(0);
  for (unsigned int i = 0, j = vch.size()-1; i < sizeof(n) && j >= 4; i++, j--)
  ((unsigned char*)&n)[i] = vch[j];
  return n;
  @@ -298,7 +298,7 @@ public:
  arith_uint256 getarith_uint256() const
  {
  auto n = getuint256();
  - return Uint256ToArith(n);
  + return UintToArith256(n);
  }
  void setvch(const std::vector<unsigned char>& vch)
  