Rolling boulder traps and pacifism

If you stepped on an unknown rolling boulder trap, and that rolling boulder
hit a monster and killed it, you would be called a killer.  This makes
playing a pacifism conduct game rather difficult.
- track boulders from unknown rolling boulder traps, and don't charge/credit
hero if they kill monsters. This is done by temporarily setting otrapped on
such boulders.
- boulders from known traps are still charged/credited to the hero
- fix a couple places in ohitmon where is_poisonable wasn't checked along
with opoisoned.

src/dokick.c

@@ -1313,6 +1313,8 @@ boolean shop_floor_obj;
 	otmp->ox = cc.x;
 	otmp->oy = cc.y;
 	otmp->owornmask = (long)toloc;
+	/* boulder from rolling boulder trap, no longer part of the trap */
+	if (otmp->otyp == BOULDER) otmp->otrapped = 0;
 
 	if(impact) {
 	    /* the objs impacted may be in a shop other than