If there are no OpenCL/UMat methods calls from application.

OpenCL subsystem is initialized:
- haveOpenCL() is called from application
- useOpenCL() is called from application
- access to OpenCL allocator: UMat is created (empty UMat is ignored) or UMat <-> Mat conversions are called

Don't call OpenCL functions if OPENCV_OPENCL_RUNTIME=disabled
(independent from OpenCL linkage type)

Fix a code indent bug:   cv2.imshow("detected lines", cdst)

- fix compilation on Apple (undefined 'oclpath')
- don't warn on OPENCV_OPENCL_RUNTIME=disabled

Entries with the same platform name, the same device name and with different driver versions
are assumed obsolete.

Following were the errors in the digits_video.py
     1 ) The code was not working because data type of x was float however in "cv2.rectangle" we require integer .
     2 ) After pressing the "esc" button the image windows did not destroy
So I amended following things:
     1 ) ~converted data type of x to int.~ Used Python integer division (//)
     2 ) used cv2.destroyAllWindows() to close all windows after the press of "esc" by user.

* Adding threading in calibrate.py

* samples: update calibrate.py

It allows umat buffers used in net forward interface
Signed-off-by: Li Peng <peng.li@intel.com>

remove unused macros and half definition macros,
also remove unused ocl::Queue
Signed-off-by: Li Peng <peng.li@intel.com>

Prevents access data after the end of input buffer near 4K page boundaries

Tests are usually lauched from source directory, so additional unnecessary
files should be eliminated.

Alternative ways (command line):
- python -B ...
- PYTHONDONTWRITEBYTECODE=1 python ...

Usage example (bash):
$ OPENCV_PYTEST_FILTER=test_digits python test.py -v