dxorshift: random number generators from the extended Xorshift family

[Joseph Rushton Wakeling via Digitalmars-d-announce]

On Sunday, 15 May 2016 at 15:15:30 UTC, Basile B. wrote:
> I confirm that all of them are run. As in your original paste. 
> All pass, 100% coverage. No problem. Anyway, NVM I should just 
> take care of my own buisness...

Ah, interesting.  I think you may have discovered a bug in 
`isForwardRange`, because that test _should_ have detected that, 
if BaseRNG is a forward range, the RNG accessed via `alias this` 
is also `save`able.

     static assert(!is(typeof(SafeRNG.save)));

... works, however.

Thank you very much for the suggestions here -- you showed up a 
nasty hole in the existing tests.