message: restore virtual for dynlibboard
diff: @@ -47,9 +47,9 @@ public:
  DynLibBoard (int board_id, struct BrainFlowInputParams params);
  virtual ~DynLibBoard ();
  - int prepare_session () override;
  - int start_stream (int buffer_size, const char *streamer_params) override;
  - int stop_stream () override;
  - int release_session () override;
  - int config_board (std::string config, std::string &response) override;
  + virtual int prepare_session () override;
  + virtual int start_stream (int buffer_size, const char *streamer_params) override;
  + virtual int stop_stream () override;
  + virtual int release_session () override;
  + virtual int config_board (std::string config, std::string &response) override;
  };
  