std.unittests for (final?) review

[bearophile]

Jonathan M Davis:

> Other changes that some people have expressed interest in are things like having 
> it printed when a test passes, and those should not be in the language or 
> druntime itself. That's going to either have to be in helper functions that are 
> run inside of unittest blocks or it's going to need to be possible to run 
> unittest blocks externally somehow

Few hooks may help. Built-in unit tests may call few things that are usually empty (the calls may contain a string with the unit test name, and other data). A unit test library is then free to fill those with code that shows statistics, prints, GUIs, etc.

Bye,
bearophile