Added new Intel-optimized 3x3 and 5x5 kernels to medianFilter.cl file and corresponding code to host in smooth.cpp

Only Intel platform and 1 channel images are supported.
Optimize OpenCL LUT function
Use 4 pixels for one unit. Some ocl code refactoring
Optimize OpenCL LUT function
Optimize OpenCL LUT function
Fix some errors
Fix some errors
Optimize openCL version of reduce function
Change buffer cols count from 64 to 32
fix code in the kernel
Fix some errors
Removed useless multiplication by 4
Merge pull request #2792 from SpecLad:merge-2.4
Merge pull request #2793 from alalek:run_android_env
OCL: matchTemplate: changed perf test
Moved new kernels under conditional compilation to disable their build for 3-channel images; added condition to use new kernels only for images that are big enough
Merge pull request #2788 from alalek:icv_public
Updating missed defines in documentation

Updating missed defines in documentation. The new defines (in imgproc.hpp) state they have a prefix of COLOR instead of CV.
opencl opticaflow fix that enables buffer2image extension
2 fixed unassigned reshapes in em (#3674)