message: Type of qi::blank is qi::blank_type
diff: @@ -63,7 +63,7 @@ using face_vector = aligned_vector<face_index_t>;
  struct obj_grammar
  {
  using It = boost::string_ref::const_iterator;
  - using skip_t = decltype(boost::spirit::qi::blank);
  + using skip_t = boost::spirit::qi::blank_type;
  using sref_t = boost::string_ref;
  using string = std::string;
  using VV = vertex_vector;
  