Class not_isspace

external/include/backward/backward.hpp:3779–3781

  // there is no find_if_not in C++98, lets do something crappy to
  // workaround.
  struct not_isspace {
    bool operator()(char c) { return !std::isspace(c); }
  };
  // and define this one here because C++98 is not happy with local defined
  // struct passed to template functions, fuuuu.
  struct not_isempty {