fix compiling error : lib/libopencv_world.a, refer to the opencv/modules/non-free/CMakefiles.txt
/usr/bin/ar: ../ocl/CMakeFiles/opencv_ocl.dir/__/__/__/out/openCV/2.4.x-static/modules/ocl/opencl_kernels.cpp.o: No such file or directory
openCL should be supported first by
sudo aptitude install nvidia-opencl-dev nvidia-cuda-doc
sudo aptitude install freeglut3-dev build-essential libx11-dev libxmu-dev \
	libxi-dev libglu1-mesa libglu1-mesa-dev