Fixes time zone issues when running on Windows

Fixes time zone issues when running on Windows

TimeZoneInfo.GetDaylightChanges() didn't work as expected when run against the
time zone data available in Windows.

This patch also enables most of the time zone related tests that were
previously ignored when not run on Unix platforms. Time zone ids will now be
mapped from tz db time zone names to Windows time zone names when needed so
that most of the tests can be run on Mono on Windows as well.