Xoroshiro pseudo-random number generator.

This is a version of the xoroshiro PRN generator with 36-bit output.
The 2⁷²-1 period coefficients in prim.txt were graciously provided by
Sebastiano Vigna.

https://vigna.di.unimi.it/ftp/papers/ScrambledLinear.pdf

src/lars/xorosh.2

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+.begin xoroshiro
+
+xstate:	-1,, ? 1
+
+parm.a==2
+parm.b==9
+parm.c==5
+parm.r==11.
+
+xoroshiro:
+	push p,t
+	move t,xstate
+	xorm t,xstate+1
+	rot t,parm.a
+	xor t,xstate+1
+	movem t,xstate
+	move t,xstate+1
+	lsh t,parm.b
+	xorm t,xstate
+	move t,xstate+1
+	rot t,parm.c
+	movem t,xstate+1
+	pop p,t
+	move a,xstate
+	add a,xstate+1
+	rot a,parm.r
+	add a,xstate
+	popj p,
+
+.end