Merge pull request #10959 from alalek:cmake_ocl4dnn

diff --cc modules/dnn/src/layers/convolution_layer.cpp
Simple merge

diff --cc modules/dnn/src/layers/pooling_layer.cpp
Simple merge

diff --cc modules/dnn/src/ocl4dnn/include/common.hpp
Simple merge

diff --cc modules/dnn/src/ocl4dnn/include/math_functions.hpp
Simple merge

diff --cc modules/dnn/src/ocl4dnn/include/ocl4dnn.hpp
Simple merge

diff --cc modules/dnn/src/ocl4dnn/src/ocl4dnn_conv_spatial.cpp
Simple merge