filter2D IPP runtime check;

* Solve issue 7676

* I7676 bis

* Aravis: fixing releasing object when no communication with camera is possible

* Removing unnecessary include

Results are not bit-exact

Don't process keypoints near border, because after rotation border points
have contrast gradients with rotation border fill.

This ocl kernel is 46%~171% faster than current laplacian 3x3
ocl kernel in the perf test, with image format "CV_8UC1".
Signed-off-by: Li Peng <peng.li@intel.com>

OpenVX C++ wrappers docs (#7681)

* adding wrapper headers to the project to see them in IDE project explorer

* readme

* doxygen: toplevel brief-s

* more doxygen

* more doxygen

https://github.com/opencv/opencv/issues/7590

happens on msys2 with gcc 6.2.0
see also http://stackoverflow.com/questions/38552221/undefined-reference-to-cvredirecterror-while-creating-shared-build-of-opencv-3

Change contour test images to be very wide (#7464)

* Change contour test images to be very wide (#7409, #7458)

Unfortunately, slows down the tests.

* Decrease the number of contour test cases, in order to (at least partially) offset the test run duration increase caused by making the test images wider

* Don't test with very wide images on 32-bit architectures

It improves 108%~230% performance in the perf test
with image format "CV_8UC1" and kernel size 3.
Signed-off-by: Li Peng <peng.li@intel.com>