[tz] Deprecating tzsetwall

[enh]

sgtm. we don't expose tzsetwall in Android.

On Tue, Apr 21, 2020 at 5:30 PM Paul Eggert <eggert at cs.ucla.edu> wrote:
>
> In reviewing the tzdb web pages for bad links and suchlike, I noticed that
> they're still talking about UNIX SVR2 (superseded since 1988) and tzsetwall. So
> I looked into tzcode's implementation of tzsetwall, and noticed that it does
> nothing useful because functions like localtime now call tzset (as POSIX has
> require for many years), thus undoing tzsetwall's effect.
>
> Since nobody evidently cares whether tzsetwall works, we should remove it. Not
> right away of course, but we can document it as deprecated now without changing
> the implementation, and remove it in a future tzcode release. So I installed the
> attached patch to do that. Comments welcome as usual.