message: Add is_stopped_flag and fix formatting
diff: @@ -51,6 +51,10 @@ public:
  /// buffered elements.
  static constexpr int is_shutting_down_flag = 0x0002;
  + /// Denotes whether the manager has already stopped. Calling member functions
  + /// such as stop() or abort() on it no longer has any effect.
  + static constexpr int is_stopped_flag = 0x0004;
  +
  // -- member types -----------------------------------------------------------
  using inbound_paths_list = std::vector<inbound_path*>;
  @@ -148,16 +152,21 @@ public:
  return getf(is_shutting_down_flag);
  }
  + /// Returns whether this manager has already stopped.
  + bool stopped() const noexcept {
  + return getf(is_stopped_flag);
  + }
  +
  /// Returns whether this stream remains open even if no in- or outbound paths
  /// exist. The default is `false`. Does not keep a source alive past the
  /// point where its driver returns `done() == true`.
  - inline bool continuous() const noexcept {
  + bool continuous() const noexcept {
  return getf(is_continuous_flag);
  }
  /// Sets whether this stream remains open even if no in- or outbound paths
  /// exist.
  - inline void continuous(bool x) noexcept {
  + void continuous(bool x) noexcept {
  if (!shutting_down()) {
  if (x)
  setf(is_continuous_flag);
  @@ -167,7 +176,7 @@ public:
  }
  /// Returns the list of inbound paths.
  - inline const inbound_paths_list& inbound_paths() const noexcept{
  + const inbound_paths_list& inbound_paths() const noexcept {
  return inbound_paths_;
  }
  @@ -179,7 +188,7 @@ public:
  bool inbound_paths_idle() const noexcept;
  /// Returns the parent actor.
  - inline scheduled_actor* self() {
  + scheduled_actor* self() {
  return self_;
  }
  