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

[Paul Eggert]

Brian Inglis wrote:

> It is not immediately apparent this is a zone "abbreviation", could be some kind
> of correction or a lat/long.

This format should be apparent in context.  In a traditional date-time stamp 
such as POSIX C-locale 'date' output ("Mon Feb 15 03:18:46 +04 2016"), the "+04" 
is not reasonably interpreted to be a latitude or longitude. True, it might be 
interpreted to be a time correction; but that would be OK as it _is_ a time 
correction.

 > Without at least minutes and possibly also a colon, this does not look like a
 > zone value.

POSIX does not allow a colon, but we could append minutes, e.g., "+0400" instead 
of "+04". Such a notation is widely used, e.g., Internet RFC 5322, which is used 
by this very email's "Date:" line (where "-0800" denotes my current time zone).

ISO 8601 allows both "+04" and "+0400" (as well as "+04:00" and some other 
possibilities excluded by POSIX).

> With more characters this may not fit within TZNAME_MAX limits, although looking around
> implementations there seems favour for 6.

POSIX requires that TZNAME_MAX must be at least 6, so we should be OK here.

The attached additional patch would change the new zone to use "+0400" rather 
than "+04". Still, I mildly prefer "+04", as it's briefer. No matter what we 
switch to, we will confuse some people; and other things being roughly equal, 
briefer is better.
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