Proposal for fixing dchar ranges

[bearophile]

Walter Bright:

> In the last couple days, we also wound up annoying a valuable 
> client with some minor breakage with std.json, reiterating how 
> important it is to not break code if we can at all avoid it..

There are still some breaking changed that I'd like to perform in 
D, like deprecating certain usages of the comma operator, etc.

Bye,
bearophile