DateTimeZone.GetOffsetFromUtc is conceptually equivalent to the BCL
TimeZoneInfo.GetUtcOffset. There's no particular *reason* for the names to
differ, and the existing Noda Time one isn't desperately better than the BCL
name.
We should work out what we're going to do and do it before v1. (It'll be pretty
simple to do if we want to, but it must be done before v1.)