Based on 8f0084ac: core/ndstrides: implement np_array()
It also checks for inconsistent dimensions if the input is a list.
e.g., rejecting `[[1.0, 2.0], [3.0]]`.
However, currently only `np_array(<input>, copy=False)` and `np_array
(<input>, copy=True)` are supported. In NumPy, copy could be false,
true, or None. Right now, NAC3's `np_array(<input>, copy=False)` behaves
like NumPy's `np.array(<input>, copy=None)`.
- Change CSlice to use `void*` for better pointer compatibility
- Only include impl *.hpp files in irrt.cpp
- Refactor typedef to using declaration
- Add missing ``// namespace`
