fixed overflow for cv::norm NORM_L2
added mask support to cv::norm, cv::meanStdDev
fixed case with zero mask
core/ocl: runtime, remove unused declarations
Merge pull request #2105 from ilya-lavrenov:norm
added OpenCL accelerated warpers
replaced Mat by Input/Output arrays
updated docs according to the last changes
Merge pull request #2112 from ilya-lavrenov:tapi_stitching
Merge pull request #2135 from alalek:ocl_runtime_cleanup_2