[tz] Split America into North America and South America

[Paul Eggert]

On 2023-01-06 16:16, Benjamin Drung wrote:
> tzselect is using zone1970.tab and iso3166.tab to construct the
> questions? How is the mapping of continents -> countries generated?

By combining zone1970.tab's first column with the continents in its 
third column. There's no need to maintain a separate table. Also see the 
comments at the end of zone1970.tab, though these are experimental.