[tz] [PROPOSED 2/2] strftime: conform better to POSIX+

[Robert Elz]

    Date:        Fri, 14 Aug 2020 15:48:28 -0700
    From:        Paul Eggert <eggert at cs.ucla.edu>
    Message-ID:  <4e86e8ac-767c-1d63-15a1-83ed3fb4b5e9 at cs.ucla.edu>

  | If this is the sort of thing portable code needs to do in order
  | to determine whether mktime has succeeded, then mktime's API
  | needs improving.

It is actually more than that, struct tm has outlived its useful
lifetime, and because of the way it is used there's no really good
way to extend it - we need a whole new struct, and a whole set of
new functions to deal with it.   Attempting to make minor improvements
to what we have now isn't worth the effort.

kre