message: Use launch_thread API in the new middleman
diff: @@ -28,14 +28,10 @@ middleman::~middleman() {
  void middleman::start() {
  if (!get_or(config(), "caf.middleman.manual-multiplexing", false)) {
  - mpx_thread_ = std::thread{[this] {
  - CAF_SET_LOGGER_SYS(&sys_);
  - detail::set_thread_name("caf.net.mpx");
  - sys_.thread_started();
  + mpx_thread_ = sys_.launch_thread("caf.net.mpx", [this] {
  mpx_.set_thread_id();
  mpx_.run();
  - sys_.thread_terminates();
  - }};
  + });
  } else {
  mpx_.set_thread_id();
  }
  