defs.h:
	add new RG_xxx entry to enum REGIONTYPE

map.c:
	initmap():  define via new "addregiontype()" call
	OPTIONAL: initmaplayout():  define at least one regionoutline

	finalisemap():
		define up/down stair types for this map


	create new habitats if required.

text.c:
	update getregionname()