[tz] make error

[Robert Elz]

    Date:        Thu, 16 Nov 2023 13:50:59 -0800
    From:        Guy Harris via tz <tz at iana.org>
    Message-ID:  <B624A0FE-A94C-480F-8674-56D471E2104C at sonic.net>


  | what is the environment Alois is using defining restrict as?

It almost certainly isn't defining it as anything (which would be why
the change without the && "!defined restrict" worked - though that would
only help if it was #defined, not defined some other way) - the
error message that was shown clearly indicates that the compiler considered
"restrict" to simply be a variable name (and then complained when it was
used as the name for two different parameters - while giving var names in
prototypes is unusual, as they accomplish nothing, it isn't prohibited, and
if present they need to make sense, which having the same name twice, doesn't).

That's what a compiler for a version of C from before "restrict" was
added would naturally assume was happening.

This does suggest though that for something like tzcode, which is used
everywhere, requiring C99 anytime soon might be a mistake (where soon
might mean any time this decade - at least).

kre