message: Fix compilation with Boost 1.66
diff: @@ -81,7 +81,11 @@ struct WorkerPool {
  // the io_service we are wrapping
  boost::asio::io_service service;
  boost::asio::io_service::work working;
  +#if BOOST_VERSION < 106600
  boost::asio::strand strand;
  +#else
  + boost::asio::io_context::strand strand;
  +#endif
  };
  inline void
  