Function executor_binder

3rd/asio-1.24.0/include/asio/bind_executor.hpp:292–296

   */
  template <typename U>
  executor_binder(executor_arg_t, const executor_type& e,
      ASIO_MOVE_ARG(U) u)
    : base_type(e, ASIO_MOVE_CAST(U)(u))
  {
  }

  /// Copy constructor.
  executor_binder(const executor_binder& other)