message: Use raw string literals for XML
diff: @@ -3951,10 +3951,10 @@ std::ostream &operator<<(std::ostream &out, const QuadratureFunction &qf)
  void QuadratureFunction::SaveVTU(std::ostream &out, VTKFormat format,
  int compression_level) const
  {
  - out << "<VTKFile type=\"UnstructuredGrid\" version=\"0.1\"";
  + out << R"(<VTKFile type="UnstructuredGrid" version="0.1")";
  if (compression_level != 0)
  {
  - out << " compressor=\"vtkZLibDataCompressor\"";
  + out << R"( compressor="vtkZLibDataCompressor")";
  }
  out << " byte_order=\"" << VTKByteOrder() << "\">\n";
  out << "<UnstructuredGrid>\n";
  @@ -4003,7 +4003,7 @@ void QuadratureFunction::SaveVTU(std::ostream &out, VTKFormat format,
  // Write cells (each cell is just a vertex)
  out << "<Cells>\n";
  // Connectivity
  - out << "<DataArray type=\"Int32\" Name=\"connectivity\" format=\""
  + out << R"(<DataArray type="Int32" Name="connectivity" format=")"
  << fmt_str << "\">\n";
  for (int i=0; i<np; ++i) { WriteBinaryOrASCII(out, buf, i, "\n", format); }
  @@ -4013,7 +4013,7 @@ void QuadratureFunction::SaveVTU(std::ostream &out, VTKFormat format,
  }
  out << "</DataArray>\n";
  // Offsets
  - out << "<DataArray type=\"Int32\" Name=\"offsets\" format=\""
  + out << R"(<DataArray type="Int32" Name="offsets" format=")"
  << fmt_str << "\">\n";
  for (int i=0; i<np; ++i) { WriteBinaryOrASCII(out, buf, i, "\n", format); }
  if (format != VTKFormat::ASCII)
  @@ -4022,7 +4022,7 @@ void QuadratureFunction::SaveVTU(std::ostream &out, VTKFormat format,
  }
  out << "</DataArray>\n";
  // Types
  - out << "<DataArray type=\"UInt8\" Name=\"types\" format=\""
  + out << R"(<DataArray type="UInt8" Name="types" format=")"
  << fmt_str << "\">\n";
  for (int i = 0; i < np; i++)
  {
  