message: If not specified, use unspecified binding
diff: @@ -170,7 +170,7 @@ auto make_kernel_params(
  vec4 const& ambient_color = vec4(0.0)
  )
  -> kernel_params<
  - normals_per_vertex_binding,
  + unspecified_binding,
  unspecified_binding,
  Primitives,
  vector<3, typename scalar_type<typename std::iterator_traits<Primitives>::value_type>::type>*,
  @@ -283,7 +283,7 @@ auto make_kernel_params(
  )
  -> kernel_params<
  NormalBinding,
  - colors_per_vertex_binding,
  + unspecified_binding,
  Primitives,
  Normals,
  TexCoords,
  