defs.h:
add F_WHATEVER
io.c:
update makedesc_ob() for when an object confers this property
update showlfstats() to show temporarily gaining the property
update makedesc_race() to show the property as a racial characteristic
(strength/bonus)
update announceflaggain() to describe adding it
update announceflagloss() to describe losing it
then make it do something!
