Request for warnings on implicit bool to int conversions

[Paolo Carlini]

Hi,
> It would be nice if there was a
>
>   -Wimplicit_bool
>
> that was enabled in -Wall which complained about these sorts of 
> operations.  In particular
> it would warn any time a bool was implicitly promoted to an int.
first blush your message should be a Bugzilla PR, this way the request 
doesn't risk to get lost and knowledgeable people could carefully 
analyze it in due course.

Thanks,
Paolo.