Girder health/laserkill fix

Allows girders to be broken by repeated laser shots to stop abuse against laserfire. Also, for actually being able to lase through walls if they're open.

Resolves issue #3796

code/game/objects/structures/girders.dm

@@ -4,6 +4,18 @@
 	density = 1
 	layer = 2
 	var/state = 0
+	var/health = 200
+
+
+	bullet_act(var/obj/item/projectile/Proj)
+		if(istype(Proj, /obj/item/projectile/beam))
+			health -= Proj.damage
+			..()
+			if(health <= 0)
+				new /obj/item/stack/sheet/metal(get_turf(src))
+				del(src)
+
+			return
 
 	attackby(obj/item/W as obj, mob/user as mob)
 		if(istype(W, /obj/item/weapon/wrench) && state == 0)
@@ -183,10 +195,12 @@
 /obj/structure/girder/displaced
 	icon_state = "displaced"
 	anchored = 0
+	health = 50
 
 /obj/structure/girder/reinforced
 	icon_state = "reinforced"
 	state = 2
+	health = 500
 
 /obj/structure/cultgirder
 	icon= 'icons/obj/cult.dmi'
@@ -194,6 +208,7 @@
 	anchored = 1
 	density = 1
 	layer = 2
+	var/health = 250
 
 	attackby(obj/item/W as obj, mob/user as mob)
 		if(istype(W, /obj/item/weapon/wrench))
@@ -220,6 +235,14 @@
 		if(prob(40))
 			del(src)
 
+	bullet_act(var/obj/item/projectile/Proj) //No beam check- How else will you destroy the cult girder with silver bullets?????
+		health -= Proj.damage
+		..()
+		if(health <= 0)
+			new /obj/item/stack/sheet/metal(get_turf(src))
+			del(src)
+
+		return
 
 	ex_act(severity)
 		switch(severity)