also add comments explaining the change

OpenCV 3.4.1

Signed-off-by: Li Peng <peng.li@intel.com>

* ave pooling ocl fix

support the padded area control in ave pooling
Signed-off-by: Li Peng <peng.li@intel.com>

* warning fix: ununitialized field

FFmpeg: 3.3.4 -> 3.4.2
LibVPX: 1.6.1 -> 1.7.0
OpenH264: 1.6.0 -> 1.7.0

Signed-off-by: Li Peng <peng.li@intel.com>

It fixes tensorflow ocl testcase of MobileNetSSD and Inception_v2_SSD
Signed-off-by: Li Peng <peng.li@intel.com>

reuse av_guess_sample_aspect_ratio() if available in ffmpeg

Existed includes sequence:
- utility.hpp -> core.hpp -> operations.hpp

cuda_fast : multi stream safety (#10906)

* CUDA_Features2D/FAST Asynchronous test

* cuda_fast : multi stream safety

* Use parallel_for instead of OpenMP

* make tmpRow proper size before copyTo to avoid reallocated tmpCol

* do the transposition without creating temporary array; replace TAB with spaces.

* revert the previous commit

> cap_ffmpeg_impl.hpp:1710:11: error: 'uchar' does not name a type

about BYPRODUCTS bin/opencv-340.jar