[tz] A small first step in merging NetBSD changes into tzcode

[Paul Eggert]

On 2023-01-04 23:23, Guy Harris wrote:
> strerror() dates back to C89; if you have a sufficiently old C library, either from a UN*X that predates the introduction of strerror() or modeled after the libraries of UN*Xes that predate the introduction of strerror(), you might need to provide your own strerror(), but I'm not sure whether we need to care about those old C libraries.

We shouldn't need to care, as the code assumes C89 and has been using 
strerror elsewhere for quite some time.

For programs like zdump I'd rather not bother implementing BSD's 'err' 
function (or the GNU 'error' function for that matter) on platforms that 
lack it; it's not worth the hassle given the small number of diagnostics 
we're talking about.

As you inferred, the main point of the change was to improve the quality 
of the diagnostics so that they look as good as those produced by 
NetBSD's mods that use the BSDish 'err' function.