Add a NextTransition.Scan test case to time_zone_lookup_test. (#218)
Add a NextTransition.Scan test case to time_zone_lookup_test. (#218)

Check the shape of every transition in every timezone.  This gives
extra confidence that we have interpreted the zoneinfo data correctly.
It also provides a convenient location for temporary edits to do
things like examine all the UTC offsets or zone abbreviations in use.
google/cctz,google/cctz