bug#21020: 24.4; `display-time-world' tampers with TZ

[Eli Zaretskii]

> Date: Sun, 26 Jul 2015 20:34:22 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 21020@debbugs.gnu.org, wgg2@member.fsf.org
> 
> > Also, the MS-Windows port can't entirely skip the time module any
> > more, as that module arranges for time.h to declare localtime_rz and
> > friends.
> 
> This could conflict with time.h in nt/inc/sys/, no?

Also, lib/time.h seems to want to replace 'localtime', which might
clash with 'sys_localtime' we currently use as replacement on w32.