Temporarily disable all purity for debug prints

[bearophile]

David Nadlinger:

> Related news: 
> https://github.com/D-Programming-Language/dmd/commit/ed8068f5036f88fff1603d98ebe96bb6659bceed

It's a bit disconcerting to see how important things I'm asking and arguing for for three years or more gets ignored, while this that I have barely noted gets worked on already :-)

But I am not very good at reading DMD code, so is someone able to translate to me the effects of those changes, and how to use them?

I presume this front end change is not following my suggestion (of adding a switch to disable purity), but adds a dirty hack that allows impure debug code inside pure functions. If this is true, then let's now find the bad side effects of this change.

Bye,
bearophile