Prevent grabcut, houghcircles and houghlines python2 demos from running automatically while browsing demos in the demo list viewer

the service has been closed since 2013/2014

otherwise model is only ever trained with default
parameters, and digits_adjust does nothing (for example)

finished with NV12 support for D3D11-interop. Now, if texture is in NV12 format then it will be converted to/from BGR UMat.

fixed issues with ocl nv12 cvt kernel

finisged ocl nv12-to-rgba kernel, update dx-interop samples. (ocl rgba-to-nv12 kernel will be added later)

an attempt to fix build issue

fix for non opencl build issue

fix typo

fix compilation warnings

fix compile issue for Mac (OpenCL)

add convertion from rgba to nv12 (still need to debug kernel)

remove empty line at the EOF

fixed compilation warning