[tz] make error

[Robert Elz]

    Date:        Thu, 16 Nov 2023 23:23:41 -0800
    From:        Paul Eggert <eggert at cs.ucla.edu>
    Message-ID:  <588e4312-2e83-4978-b236-642961ca41c3 at cs.ucla.edu>

  | On 2023-11-16 21:04, Robert Elz via tz wrote:
  | > This does suggest though that for something like tzcode, which is used
  | > everywhere, requiring C99 anytime soon might be a mistake
  |
  | Not sure this particular example suggests that, as Alois merely needs to 
  | compile with --std=gnu11 (or --std=gnu99 or -DPORT_TO_C89 or whatever).

I wasn't suggesting a problem with the current distribution, that -D is
a simple workaround (but expecting a gnuXX to work isn't - not everything
is gcc), but in your earlier message you quotes the 2023a NEWS:

     The two new macros are transitional aids planned to be removed in a
     future version, when C99 or later will be required.

and my point was just that that future version probably ought to be
rather distant future, not next year sometime (or even the next few years
after that).

It might be worth adding a "common issues" file (with some rational name,
not that) that people can look in, if things don't simply work first time,
if for nothing else, to avoid needing to send queries to this list.

kre