message: Add a warning in Mesh::EnsureNodes if converting a NURBS mesh
  to a high-order, H1-conforming mesh.
diff: @@ -5289,6 +5289,25 @@ void Mesh::EnsureNodes()
  else // Mesh using a legacy FE_Collection
  {
  const int order = GetNodalFESpace()->GetElementOrder(0);
  + if (NURBSext)
  + {
  +#ifndef MFEM_USE_MPI
  + const bool warn = true;
  +#else
  + ParMesh *pmesh = dynamic_cast<ParMesh*>(this);
  + const bool warn = !pmesh || pmesh->GetMyRank() == 0;
  +#endif
  + if (warn)
  + {
  + MFEM_WARNING("converting NURBS mesh to order " << order <<
  + " H1-continuous mesh!\n "
  + "If this is the desired behavior, you can silence"
  + " this warning by converting\n "
  + "the NURBS mesh to high-order mesh in advance by"
  + " calling the method\n "
  + "Mesh::SetCurvature().");
  + }
  + }
  SetCurvature(order, false, -1, Ordering::byVDIM);
  }
  }
  