message: external_example: fix compile errors
diff: @@ -20,7 +20,7 @@ void ExampleImpl::init()
  _parent->register_mavlink_message_handler(
  MAVLINK_MSG_ID_HEARTBEAT,
  - std::bind(&ExampleImpl::process_heartbeat, this, _1), (void *)this);
  + std::bind(&ExampleImpl::process_heartbeat, this, _1), this);
  }
  @@ -31,14 +31,14 @@ void ExampleImpl::deinit()
  void ExampleImpl::say_hello() const
  {
  - Debug() << "Hello world, I'm a new plugin.";
  + LogInfo() << "Hello world, I'm a new plugin.";
  }
  void ExampleImpl::process_heartbeat(const mavlink_message_t &message)
  {
  UNUSED(message);
  - Debug() << "I received a heartbeat";
  + LogDebug() << "I received a heartbeat";
  }
  