message: gapi: fix visibility conflict in OpenCV builds
diff: #ifndef OPENCV_GAPI_OWN_TYPES_HPP
  #define OPENCV_GAPI_OWN_TYPES_HPP
  -# if 0
  +# if defined(__OPENCV_BUILD)
  # include <opencv2/core/base.hpp>
  # define GAPI_EXPORTS CV_EXPORTS
  