[tz] McMurdo/South Pole

[Paul Eggert]

Stephen Colebourne wrote:
> I'm simply asking the tzdb to provide
> reasonable local time information since the start of global offset
> fixing for the IDs it provides

That's being done for McMurdo -- as far as we know, its
entry is accurate for all time stamps used since it was
founded, and (as Russ Allbery pointed out) for time stamps
before McMurdo was founded and for which localtime is undefined,
it's reasonable to interpret the new entry as being more
"accurate" than the old.

> keeping the data stable if entries are guesswork.

That's not a reasonable request even for near-future
time stamps that end users actually care about, much
less for these long-ago time stamps for uninhabited
locations, where they don't care.

We're about to change near-future data (even though our
changes are guesswork) for Tocantins and for Jordan.
This is not because we *like* making guesses; it's because
guessing is the best we can *do*, the system does not
allow us to refuse to make these guesses, and
better guesses are preferable to worse guesses.