implicit declaration in C++ considered harmful

[Joe Buck]

> > I think EGCS should be standard conforming and flags implicit
> > declaration as an error not a warning.
> 
> The C and C++ standards don't distinguish errors and warnings,
> though I say this with somewhat less than full confidence because
> I'm not as familiar with the C++ draft as with the C standard.

Yes, we technically comply, but nevertheless the current behavior
is not desirable.