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

[Eli Zaretskii]

> Date: Sun, 26 Jul 2015 10:05:38 -0700
> From: Paul Eggert <eggert@cs.ucla.edu>
> CC: wgg2@member.fsf.org, 21020@debbugs.gnu.org
> 
> > I hope we have some
> > tests to make sure this doesn't cause any regressions.
> 
> test/automated/icalender-tests.el exercises the new code.

But the tests there that play with TZ are all expected failures on
MS-Windows, because they use Posix format of time-zone definition that
Windows runtime doesn't support.  So that probably means there are no
tests that could be used on Windows.

> 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?