refactored filters in the ocl module; added an accuracy tests for ocl::medianFilter
Updated ffmpeg_vesion.cmake after #1516.
Merge pull request #1626 from ilya-lavrenov:ocl_filters
Merge pull request #1640 from alalek:ocl_fix_exp_test
added Khronos OpenCL 1.2 header files
ocl: force to use Khronos OpenCL headers
ocl: update autogenerated code