It now makes no assumptions about the terrains that might be defined in the base scenario.
* The existing terrain in the base's outdoors (previously ignored entirely) is now partitioned into 9 segments and plopped down to form the border of the new scenario's outdoors.
* It treats the locations (23,23) amd (24,24) specially, assuming they contain a sign and a town respectively. These are left as-is in the top left sector but replaced with the base ground in every other sector.
* Since there are now two separate bases, one for cave and one for surface, no substitution of terrain is done in the starter town.
