message: Fix ffmpeg detection with -D OPENCV_WARNINGS_ARE_ERRORS=ON option.
diff: @@ -15,12 +15,15 @@ static void test()
  AVFormatContext* c = 0;
  AVCodec* avcodec = 0;
  AVFrame* frame = 0;
  + (void)avcodec;
  + (void)frame;
  #if LIBAVFORMAT_BUILD >= CALC_FFMPEG_VERSION(52, 111, 0)
  int err = avformat_open_input(&c, "", NULL, NULL);
  #else
  int err = av_open_input_file(&c, "", NULL, 0, NULL);
  #endif
  + (void)err;
  }
  int main() { test(); return 0; }
  