[tz] Bug in tzdata2012c/northamerica 2x Idaho County in America/Los_Angeles

[Zefram]

Steve Jones wrote:
>It might be be more accurate to say "northeastern three-quarters of
>Idaho county", given the portion of the America/Boise rule which juts
>northwards to the west of the Salmon River.

Looks like it could be even more usefully (and just as succinctly)
described as "Idaho county northeast of Salmon River".

-zefram