message: remove clang warning
diff: namespace RINGMesh
  {
  const std::array< std::array< index_t, 3 >, 4 >
  - Geometry::Tetra::tetra_facet_vertex = { { { 1, 3, 2 }, { 0, 2, 3 },
  - { 3, 1, 0 }, { 0, 1, 2 } } };
  + Geometry::Tetra::tetra_facet_vertex = { { { { 1, 3, 2 } }, { { 0, 2, 3 } },
  + { { 3, 1, 0 } }, { { 0, 1, 2 } } } };
  double dot_perp( const vec2& v0, const vec2& v1 )
  {
  