Made undeath contagious (depending on rule settings, of course):
Soldiers of type IT_MAN slain by soldiers of type IT_UNDEAD now have
an UNDEATH_CONTAGION % chance of rising back to life as undead in the
unit that had the undead that created them (or as monsters, if the
unit that created them was killed off).  The type of undead is
approximately 33% undead and 66% skeletons.