Create structured dtype from a 2d ndarray with unstructured dtype.

def inflate_dtype(arr, names):
    """Create structured dtype from a 2d ndarray with unstructured dtype."""
    arr = np.asanyarray(arr)
    if has_structured_dt(arr):
        return arr.dtype
    s_dt = arr.dtype
    dt = [(n, s_dt) for n in names]
    dt = np.dtype(dt)
    return dt