Notice/Warning on narrowStrings .length

[bearophile]

James Miller:

> Another option would be to have some sort of general lint tool 
> that picks up on these kinds of potential errors, though that 
> is a lot bigger scope...

Lot of people in D.learn don't even use "-wi -property" so go 
figure how many will use a lint :-)

In first approximation you can rely only on what people see 
compiling with "dmd foo.d", that is the most basic compilation 
use only. More serious programmers thankfully activate warnings.

Bye,
bearophile