fix test_cuda_elementwise_small, after removing `using namespace std`
fix test_cuda_elementwise_small, after removing `using namespace std`

hughperkins/coriander,hughperkins/coriander,hughperkins/coriander,hughperkins/cuda-on-cl,hughperkins/cuda-on-cl,hughperkins/coriander,hughperkins/cuda-on-cl,hughperkins/cuda-on-cl