package/xxhash: bump to version 0.8.1

- Drop first patch (already in version)
- Refresh upstream status of latest patch
- Update hash of LICENSE and add cli/COPYING:
  https://github.com/Cyan4973/xxHash/commit/85e1ea2ab0d90463b804f4a65b0f67d99718c6f8

https://github.com/Cyan4973/xxHash/releases/tag/v0.8.1



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>