update countres and capitals in quiz(6)

update countres and capitals in quiz(6)

Changes:
- update country and capital names that have changed in recent years
- remove the formal prefix from South Africa for consistency with other
  country names
- add additional capitals for countries with multiple capitals
- add "The" as optional prefix for The Gambia and The Bahamas
- add missing suffix "City" to a few capitals
- add many missing countries

NetBSD appears to have also added territories which I've not added in this
update.

The removal of The Hague for The Netherlands was taken from NetBSD and
confirmed by otto@

The duplicate Turkey and Georgia entries have not been touched.

Prompted by a diff by Ben Fuller, who also provided much helpful feedback.