Added clamp() for THRESH_TRUNC mode
optimized stitching warpers
A more efficient workaround for erode
Optimized memory access by using stride pattern
Fixed several problems found by PVS-Studio.

This fixes all problems from the article "Checking OpenCV with PVS-Studio"
<http://www.viva64.com/en/b/0191/> that are not already fixed and are
not in 3rdparty or the legacy module.

The problems fixed are two instances of useless code and one instance
of unspecified behavior (right-shifting a negative number).
optimized cv::repeat
run.py: added --android_env parameter
run.py: propagate OPENCV* env variables only with --android_propagate_opencv_env flag
Optimize openCL version of reduce function
Change buffer cols count from 64 to 32
fix code in the kernel
Fix some errors
Merge pull request #2793 from alalek:run_android_env
2 fixed unassigned reshapes in em (#3674)
Merge pull request #2796 from berak:b_3674_24
optimized cv::meanStdDev
Merge pull request #2771 from SpecLad:pvs-checks-opencv
added performance test
Merge pull request #2787 from ilya-lavrenov:tapi_repeat
Merge pull request #2809 from ilya-lavrenov:tapi_copy_perf