Sync zoneinfo database with tzdata2008b from elsie.
asia: 8.14 -> 8.18
backward: 8.4 -> 8.6
northamerica: 8.20 -> 8.23
southamerica: 8.18 -> 8.19
zone.tab: 8.13 -> 8.16
From Arthur David Olson's comments:
* Iraq abandons DST.
* Syria switched (from 2008 forward) to start DST at the start of the first
Friday in April and end DST at the start of October 1.
* Change Cuba (from 2008 forward) to start DST the third Sunday in March.
* Add America/Argentina/San_Luis information.
* "Saigon" zone renamed "Ho_Chi_Minh".
* "Calcutta" zone renamed to "Kolkata".