RFC: Named warnings

[Stan Shebs]

Paolo Bonzini wrote:

>What
>about -Werror-missing-prototype, -Wwarn-missing-prototype, -Wmissing-prototy
>pe, -Wno-missing-prototype?  The third would base its behavior on
>whether -Werror is specified.  This would avoid overloading -E which runs
>cpp now.
>
-Efoo seemed most concise, plus it would stand out better when
reading a long compiler line.  Right now only -E by itself is
used, so there's not really an overloading problem.  But
-Werror- is sensible too, if people would prefer to go that way.

Stan