message: In HypreParMatrix::PrintHash, skip printing of 'big_j' with older
  versions of hypre.
diff: @@ -1638,6 +1638,7 @@ void HypreParMatrix::PrintHash(std::ostream &out) const
  hf.AppendInts(csr->j, csr_nnz);
  out << hf.GetHash() << '\n';
  }
  +#if MFEM_HYPRE_VERSION >= 21600
  out << csr_name << " big j hash : ";
  if (csr->big_j == nullptr)
  {
  @@ -1648,6 +1649,7 @@ void HypreParMatrix::PrintHash(std::ostream &out) const
  hf.AppendInts(csr->big_j, csr_nnz);
  out << hf.GetHash() << '\n';
  }
  +#endif
  out << csr_name << " data hash : ";
  if (csr->data == nullptr)
  {
  