1st draft of complete class-based std.random successor

[bearophile]

Joseph Rushton Wakeling:

> Thanks for pointing me to the bug report; I'd forgotten that 
> this was an open issue :-)

In Bugzilla probably there are many bug reports/enhancement 
requests about std.random, so I suggest you to read them. Some of 
them can be useful, while other are probably already addressed in 
the current (or planned) std.random2.

Another random one that was just commented by Infiltrator:
https://d.puremagic.com/issues/show_bug.cgi?id=5901

Bye,
bearophile