bug#641: format-time-string %Z does not work, starting with Emacs 22.2

[Drew Adams]

> > IOW, we should give users _both_ possibilities 
> > unambiguously: Posix-only and possibly-non-Posix,
> > better-than-nothing, YMMV, human-readable name.
> > 
> > We can do that by introducing a new format key, in addition to %Z.
> 
> I'm okay with having a new format, or with adding a function that
> would return a time-zone name that is just a string, not the spec
> codified by Posix.  (It could return strings like "Asia/Riyadh" on
> Posix platforms.)

Great. Thanks. Either solution is fine by me.

Probably a new format is better for users (keep everything in one place), if
there are no other considerations.