[tz] A New Rule? (was McMurdo/South Pole)

[Bill Seymour]

A partly-baked idea to solve the more general problem
of when zones appear and disappear:  would it make
sense to have another kind of entry in the zone RULES
column to indicate that we should now follow another
zone's practice?  How about the keyword, Zone, a
space, and the name of the other zone, with the next
column following whitespace, if present, being the
[UNTIL] column?