[tz] Asia/Kashgar offset

[Paul Eggert]

Kashgar is like Ürümqi, in that there are two official time zones in 
use, one being +08 and the other being +06. Users who prefer +08 should 
use Asia/Shanghai. See the comments for Asia/Urumqi. For what it's 
worth, the English-language Wikipedia page for Kashgar cites the same 
time zone source that we do for Ürümqi.

By the way, if you have access reliable sources for the history of 
timekeeping in this region please let us know; most of our pre-1986 data 
are sheer guesswork.