message: core: fix visibility handling
diff: @@ -371,10 +371,10 @@ Cv64suf;
  # define OPENCV_DISABLE_DEPRECATED_COMPATIBILITY
  #endif
  -#ifdef CVAPI_EXPORTS
  -# if (defined _WIN32 || defined WINCE || defined __CYGWIN__)
  +#ifndef CV_EXPORTS
  +# if (defined _WIN32 || defined WINCE || defined __CYGWIN__) && defined(CVAPI_EXPORTS)
  # define CV_EXPORTS __declspec(dllexport)
  -# elif defined __GNUC__ && __GNUC__ >= 4
  +# elif defined __GNUC__ && __GNUC__ >= 4 && (defined(CVAPI_EXPORTS) || defined(__APPLE__))
  # define CV_EXPORTS __attribute__ ((visibility ("default")))
  # endif
  #endif
  