message: Add documentation about warning suppression in solver.
diff: @@ -25,10 +25,16 @@ namespace mfem
  using namespace std;
  -namespace detail
  +// At the time of writing this setting the print level by integer has been
  +// marked legacy. However, to ensure a reasonable level of backwards
  +// compatibility, the integer-based legacy print level is synchronized with
  +// the new class-based approach, requiring some legacy code to be used
  +// internally. Therefore the warning of using legacy is silenced in parts
  +// of this file.
  +namespace internal
  {
  -MFEM_DISABLE_WARNING_PUSH
  -MFEM_DISABLE_WARNING_DEPRECATED
  +MFEM_DISABLE_WARNING_PUSH;
  +MFEM_DISABLE_WARNING_DEPRECATED;
  }
  IterativeSolver::IterativeSolver()
  @@ -56,9 +62,9 @@ IterativeSolver::IterativeSolver(MPI_Comm comm_)
  }
  #endif
  -namespace detail
  +namespace internal
  {
  -MFEM_DISABLE_WARNING_POP
  +MFEM_DISABLE_WARNING_POP;
  }
  double IterativeSolver::Dot(const Vector &x, const Vector &y) const
  @@ -77,10 +83,10 @@ double IterativeSolver::Dot(const Vector &x, const Vector &y) const
  #endif
  }
  -namespace detail
  +namespace internal
  {
  -MFEM_DISABLE_WARNING_PUSH
  -MFEM_DISABLE_WARNING_DEPRECATED
  +MFEM_DISABLE_WARNING_PUSH;
  +MFEM_DISABLE_WARNING_DEPRECATED;
  }
  void IterativeSolver::SetPrintLevel(int print_lvl)
  @@ -136,9 +142,9 @@ void IterativeSolver::SetPrintLevel(PrintLevel options)
  #endif
  }
  -namespace detail
  +namespace internal
  {
  -MFEM_DISABLE_WARNING_POP
  +MFEM_DISABLE_WARNING_POP;
  }
  IterativeSolver::PrintLevel IterativeSolver::FromLegacyPrintLevel(
  