Update to how bonuses are calculated in chance to hit code to be

consistent across all relevant effects (treating avoidance
and hit chance bonuses equally).
Rule ArcheryHitPenalty will now calc correctly (Was doing basically nothing)
New field npc_types 'Avoidance' (add avoidance bonus to npc)
Rules for setting min / max chance to hit

zone/zonedump.h

@@ -112,6 +112,7 @@ struct NPCType
 	uint8	mount_color;	//only used by horse class
 	float	attack_speed;	//%+- on attack delay of the mob.
 	int		accuracy_rating;	//10 = 1% accuracy
+	int		avoidance_rating;	//10 = 1% avoidance
 	bool	findable;		//can be found with find command
 	bool	trackable;
 	int16	slow_mitigation;