[C++] Deprecate old for-scope handling

[Eric Gallager]

On 1/19/18, Nathan Sidwell <nathan@acm.org> wrote:
> Jason,
> what do you think about deprecating the ARM-era for-scope handling that
> allows:
>    void f ()
>    {
>      for (int i = 0;;);
>      i = 2;
>    }
>
> we noisily accept that in c++98 mode with -fpermissive.  It wasn't even
> well formed then.  Implementing this has some unique requirements in the
> name-lookup machinery, which I ran into again today.
>
> Option A: rip out now because it's a c++98 ARM-compatibility crutch
> Option B: deprecate in gcc-8 and remove in gcc-9.
>

I support Option B because it's good to let people know ahead of time
about impending removals of things

> nathan
>
> --
> Nathan Sidwell
>