Adjust pre-1926 Russian UTC offsets as per Byalokoz 1919.

(Thanks to Vladimir Karpinsky.)
* asia (Asia/Tbilisi, Asia/Samarkand):
* europe (Europe/Riga, Europe/Samara, Asia/Yekaterinburg, Asia/Omsk)
(Asia/Krasnoyarsk, Asia/Irkutsk, Asia/Yakutsk, Asia/Vladivostok):
Match Byalokoz 1919 better.
* NEWS: Document the above.