nexus/doc/add_damtype.txt

in defs.h:
	add enum
	increment MAXDAMTYPE
in objcets.c:
	update getdamname() - eg. you take 5 "electrical" damage
	update getdamnamenoun() - eg.  you are immune to "electricity"

in attack.c
	update getattackverb if required
	update getkillverb if required

	update attackob() to say whether dealing this damtype to an object
		will dull a weapon.
		ie. hitting a door with DT_CHOP won't damage the weapon
		ie. hitting a door with DT_SLASH _will_ damage the weapon