fixed many bugs related to Mat::getUMat(), asynchronous kernel execution etc. Also, played a bit with ocl::cvtColor vs cv::cvtColor performance
fixed several compile errors/warnings; reacted on the PR comments
trying to guess and fix strange failure in core test
another attempt to fix Core_UMat.getUMat test
yet another attempt to make Core_UMat.getUMat test work
try to eliminate failure in opencv_imgproc_test
still trying to fix failure in opencv_test_imgproc
hopefully, now opencv_test_imgproc should pass
dummy commit to rerun pre-commit tests
Merge pull request #1901 from vpisarev:ocl_svm3