ocl: fix cl_platform.h:95: #elif _WIN32 -> #elif defined(_WIN32)
ocl: fix cl_platform.h:95: #elif _WIN32 -> #elif defined(_WIN32)

apavlenko/opencv,apavlenko/opencv,apavlenko/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,apavlenko/opencv,apavlenko/opencv,opencv/opencv,opencv/opencv,opencv/opencv,apavlenko/opencv,opencv/opencv,opencv/opencv,opencv/opencv