message: Bugfix: PA for NonlinearForm now works in serial
diff: @@ -137,10 +137,14 @@ void NonlinearForm::Mult(const Vector &x, Vector &y) const
  const Vector &px = Prolongate(x);
  if (P) { aux2.SetSize(P->Height()); }
  + // If we are in parallel, ParNonLinearForm::Mult uses the aux2 vector.
  + // In serial, place the result directly in y.
  + Vector &py = P ? aux2 : y;
  +
  if (ext)
  {
  - ext->Mult(px, aux2);
  - aux2.HostRead();
  + ext->Mult(px, py);
  + py.HostRead();
  return;
  }
  @@ -149,7 +153,6 @@ void NonlinearForm::Mult(const Vector &x, Vector &y) const
  const FiniteElement *fe;
  ElementTransformation *T;
  Mesh *mesh = fes->GetMesh();
  - Vector &py = P ? aux2 : y;
  py = 0.0;
  