[PATCH 21.5] Fix signs in time zone string.

Marcus Crestani writes:

 > -arguments: (SECOND MINUTE HOUR DAY MONTH YEAR &optional ZONE &rest REST)
 > +arguments: (SECOND MINUTE HOUR DAY MONTH YEAR &optional ZONE)

I think this probably breaks use of several of the time functions as
arguments in the form `(apply encode-time (some-time-function))' (eg,
decode-time returns DST and DOW as well as those above).

We should take care here.

Steve