nexus/doc/add_spells.txt

defs.h:
	add the OT_xxx enum
	(optional) add a scroll to do the same effect - not for boosts though
	(optional) add a potion to do the same effect - not for boosts though

objects.c:
	define the spell
		remember to have spelllevel
	(optional) add a scroll to do the same effect, use F_LINKSPELL
	(optional) add a potion to do the same effect
	assign AI hint flags so it knows how to cast it

spell.c:
	implement the effects
		remember to fill in *seenbyplayer if there is a scroll version
	cope with:
		blessed/cursed
		target having antimagic - use hasmr(victim)
		blindness if the effect is vision-based

ai.c
	update aigetspelltarget(); (if we have target ST_SPECIAL)
	update aispellok();