Challenge: write a really really small front() for UTF8

[bearophile]

Andrei Alexandrescu:

> -w
>
> Probably time to move that from a warning to an error. In the 
> short time we've used D at Facebook (forgot to add "-w" to the 
> implicit flags) we've already have not one, but two bugs 
> related to switch's implicit fallthrough.

Lot of people in D.learn don't use warnings.
What I'd like is to have (informational) warning active on 
default, and to disable them on request with a compiler switch.

Bye,
bearophile