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

OpenCL runtime does not require OpenCL development file (libOpenCL.so),
just the "run" library (so.1).

This patch searches for the run library (so.1) if the dev library (.so)
is not found.

Web search shows that this error has been present since at least 2015
http://answers.opencv.org/question/80532/haveopencl-return-false/Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>

Templates are replaced by macro

Apple OpenCL framework hasn't OpenGL sharing extension