Added a perf. test for gpu::FarnebackOpticalFlow
Added a perf. test for gpu::FarnebackOpticalFlow

opencv/opencv,opencv/opencv,opencv/opencv,apavlenko/opencv,apavlenko/opencv,apavlenko/opencv,opencv/opencv,apavlenko/opencv,opencv/opencv,apavlenko/opencv,opencv/opencv,apavlenko/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv