SHR2A - A kind of small PRNG related to SHR3 
--------------------------------------------

This is a small 32bit prng similar to shr3,
with one less shift-xor operation, and one extra addition.

**It can pass diehard but fails badly in 2-dimensions.

``` 
 v= v ^ ( ( v << Sl ) + A )  
 v= v ^ v>>>Sr
```

Dependant on the values of constants Sl, Sr and A : **v** traces
psuedorandom walks through portions of its 32bit spaces.

The walks of a few thousand parameter combinations were mined
in a few hours, coming up with hundreds of walks that happen 
to cover over 95% of the 32bit state space.

Despite their small generation, long walks found in these formula which
set reasonably complex addition values, can appear indestinguishable 
from random streams except for a faint bias due to the likelyhood of uneven
coverage of the numberspace, which shrinks as the proportion of coverage
increases.

These values produce walks over 99.9% of the state space.
```
  va^= (va<<7)+1498916339; va^= va>>>8   //period is 4294368480 
	vb^= (vb<<6)+1973037067; vb^= vb>>>10  //period is 4294280630
	vc^= (vc<<5)+1334203894; vc^= vc>>>12  //period is 4293793381  	  
```

The walks tend to be less apparently regular than the classic
shr3 form**. 

For the purpose of providing high quality deterministic prngs for
Fdrandom.js, the best discovered formulations were checked individually
and combined by 'xor'ing to give longer period prngs with more
confidence of deeper quality.

This was was retired when an Alea like generator is much more
efficient in floating point math at least.