[tz] North Korea into +8:30 time zone

[Paul Eggert]

Robert Elz wrote:
> it is no more clear to me that
> older zic's, and other uses, will all support +0830 as the abbreviation

Older zic's support +0830, so this shouldn't be a problem.  I just now checked 
the zic from the tz-1993d edition, for example, and it works.

tzdata entries for circa 1954-1961 timestamps do use "KST" to abbreviate time in 
Korea regardless of whether it was North (+0900) or South (+0830) Korea. 
However, this was purely my invention, as far as I know it has no basis and we 
should probably fix this too at some point.  We used to be pretty loose about 
this sort of thing but we should steer the tz database in the direction of 
recording what's known instead of making stuff up.