[tz] Astrakhan region got approval to change its time zone

[Paul Eggert]

Brian Inglis wrote:

> I just know a bunch of people out there are cluelessly checking this string is
> upper case alpha.

We crossed that bridge many years ago, so we shouldn't be giving any such people 
much more grief than we're already giving them.

There have been non-upper-case-alpha abbreviations in the tz database since 
nearly day one. For example, in our repository the very first version of the 
'europe' file (dated 1986) had spaces in some abbreviations, and spaces are much 
harder to parse than digits or plus signs are. In the current release, 
Pacific/Guam uses abbreviations that are not upper case alpha.

Also, POSIX has blessed digits and plus signs in the abbreviations for quite 
some time; see <https://mm.icann.org/pipermail/tz/2001-January/011305.html>.