written in 2016 by Lapo Luchini lapo@lapo.it
based on the C sources as found on 2016-01-22 on http://xorshift.di.unimi.it/xorshift128plus.c
Written in 2014-2015 by Sebastiano Vigna (vigna@acm.org)
To the extent possible under law, the author has dedicated all copyright and related and neighboring rights to this software to the public domain worldwide. This software is distributed without any warranty.