fixed overflow for cv::norm NORM_L2
core/ocl: cleanup unused files
added mask support to cv::norm, cv::meanStdDev
fixed cv::mixChannels perf test
Merge pull request #2129 from ilya-lavrenov:mix_fix
Merge pull request #2128 from alalek:ocl_cleanup_runtime
fixed case with zero mask
Merge pull request #2105 from ilya-lavrenov:norm