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"
update wepdullable() 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
in attack.c
update isphysicaldam()
update getattackverb if required
update getkillverb if required
