Add an Actor.ai_spread_add property that reduces the accuracy of aiSeetargetPos

This is for use in movement effects that bypass actually having to follow via normal walking so they don't home in on players that break LOS too quickly.

game/engines/default/engine/interface/ActorAI.lua

@@ -259,7 +259,7 @@ function _M:aiSeeTargetPos(target, add_spread, max_spread)
 			if target.last_special_movement and LSeen.GCknown_turn and (target.last_special_movement > LSeen.GCknown_turn) then 
 				spread = max_spread  -- If the target has done a "special" movement, such as teleporting a long distance or out of LOS, max out our randomness so we don't cheat chasing them with teleports or whatever
 			else
-				spread = spread + math.min(max_spread, add_spread + math.floor((game.turn - (LSeen.GCknown_turn or game.turn)) / (game.energy_to_act / game.energy_per_tick))) -- Limit spread to 10 tiles
+				spread = spread + math.min(max_spread, add_spread + (self:attr("ai_spread_add") or 0) + math.floor((game.turn - (LSeen.GCknown_turn or game.turn)) / (game.energy_to_act / game.energy_per_tick))) -- Limit spread to 10 tiles
 			end
 			tx, ty = util.bound(tx + rng.range(-spread, spread), 0, game.level.map.w - 1), util.bound(ty + rng.range(-spread, spread), 0, game.level.map.h - 1)