`empty_like` ignores memory-order

Consider:

```
x = np.random.normal(size=(3, 5)).astype(np.float64, order="F")
x_gpu = gpuarray.to_gpu(x)
y_gpu = gpuarray.empty_like(x_gpu)
x_gpu.flags.c_contiguous == y_gpu.flags.c_contiguous # gives "False"
```

I'm not very familiar with the `ArrayFlags` mechanism. It seems to me that the problem is that `empty_like` doesn't set the `strides` argument of the `GPUArray`-constructor. But I don't know the repercussions of doing this, so I didn't send a PR.