message: Update board_controller.h
diff: extern "C"
  {
  #endif
  - // I dont use const char * because I am not sure that all
  - // languages support passing const char * instead char *
  -
  // data acquisition methods
  SHARED_EXPORT int CALLING_CONVENTION prepare_session (
  int board_id, const char *json_brainflow_input_params);
  