Regarding warnings

[bearophile]

I suggest to remove the "-w" switch from the list of dmd/ldc2 
switches, and later to remove that functionality too. It's better 
to keep only the informational warnings.

I keep seeing people in D.learn that miss warnings because they 
don't active them, so I suggest to activate informational 
warnings on default.

And then I suggest to add a switch to disable the warnings, for 
the rare situations where you don't want them.

Bye,
bearophile