ArraySegmentExtensions.CopyTo should use Buffer.BlockCopy instead of Array.Copy

[longqinsi]

For the sake of performance, the implementation of Nito.ArraySegments.ArraySegmentExtensions.CopyTo should use Buffer.BlockCopy instead of Array.Copy.

[StephenCleary]

This is only possible for blittable types, of course. I think it would make sense to put in this optimization for byte arrays.

[longqinsi]

You're right.