bug#23600: 25.1.50; encode-time returns wrong result

[Eli Zaretskii]

> Cc: kzhr@d1.dion.ne.jp, 23600@debbugs.gnu.org
> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Sat, 4 Jun 2016 15:18:43 -0700
> 
> Eli Zaretskii wrote:
> > I think it would be cleaner if we copied the string before modifying
> > it.
> 
> Other parts of Emacs modify the string in place and expect the modifications 
> to 
> affect the time zone setting, so in general it won't work to copy the string, 
> modify the copy, and pass the copy's address to putenv.

Too bad.