add input paramter checking that verifies the existance of the input files to stero_match example
Merge remote-tracking branch 'upstream/master'
Use OPENNI2_INCLUDE64 environment variable.
(Set on windows with install from http://structure.io/openni).
check input paramter by checking the image size
remove the unnecessary header file
Minor optimization for ocl_canny
fixed test for ocl WarpAffine
Correctly unrolled some cycles
Fix HoughLines crashes (Bug #3959).

Avoid phi exceed PI/2 to get the negative value of cos(phi).
fixed my_umat(roi).clone() test by disabling poorly aligned ROI's. Real fix of the problem will require a separate branch in UMat::copyTo().
Merge pull request #3397 from ElenaGvozdeva:ocl_WarpAffine_test
Merge pull request #3392 from wangyan42164:houghlines_bug_fix
Merge pull request #3357 from briansp2020:master
Merge pull request #3394 from akarsakov:ocl_canny
Merge pull request #3400 from vpisarev:fixed_umat_test_crash
fixed path to the checkerboard image
Merge pull request #3402 from vpisarev:fixed_python_tests
moved cv::partition from private.hpp to operations.hpp, to expose the function to users
Merge pull request #3403 from vpisarev:moved_partition
Set status to beta