Replace random number generation module by Xoshiro

[thomas3494]

See title. Example program of usage

use Array: all;
use StdIO: all;
use Benchmarking: all;
use Xoshiro: all;

inline
double[n], struct State256 add_normal(double[n] x, struct State256 state)
{
   for (i = 0; i + 1 < n; i += 2) {
     u1, state = xoshiro256p(state);
     u2, state = xoshiro256p(state);
     N1, N2 = to_normal(u1, u2, 0d, 1d);
     x[i]     = N1;
     x[i + 1] = N2;
   }
   if (n % 2 != 0) {
     u1, state = xoshiro256p(state);
     u2, state = xoshiro256p(state);
     N1, N2 = to_normal(u1, u2, 0d, 1d);
     x[n - 1] = N1;
   }
   return (x, state);
}

int main()
{
  n = 1000000000;
  p = 8; // number of processors you have
  states = seed_arrl(p, srand256());

  x = {iv -> 0d | iv < [p, n / p]};

	itime = getInterval("uniform", 1);
  start(itime);
  x, states = {[t] -> add_normal(x[t], _sel_VxA_([t], states))};
  end(itime);

	time, unit = returnResultUnit(itime);
  printf("Created %lf GB of N(0, 1) variables at %lf GB/s\n",
         8d * tod(n) / 1e9, 8d * tod(n) / 1e9 * 2d / time);

  return toi(sum(x));
}

Closes #113

[sbscholz]

looks fine