Daylight transitions are not correct on Unix.

Daylight transitions are not correct on Unix.

When checking whether a DateTime is daylight savings time, TimeZoneInfo gets it wrong when the AdjustmentRule spans multiple years. This is because CheckIsDst will adjust the DateTime's Year to be the same as the AdjustmentRule.StartTime.Year. On Unix, this is incorrect because the AdjustmentRules are fixed for the whole time; the offset doesn't change at all during the AdjustmentRule.

This is a fix for the last 2 issues noted in #2185.