Zombies tweaks (#5377)

After having our first zombie round, I saw some issues and came up with some solutions

-zombies can now devour their victims
-zombie transformation now properly removes people's languages
-trioxin will now revive the dead, allowing for people that were mudered by zombies to return back to life as a zombie
-attacking people already infected with the zombie transformation will send a message to the attacking zombie

code/modules/mob/living/carbon/human/species/outsider/undead.dm

@@ -187,7 +187,11 @@
 	sprint_speed_factor = 0.3
 	exhaust_threshold = 0 //No oxyloss, so zero threshold
 
-	inherent_verbs = list(/mob/living/carbon/human/proc/darkness_eyes)
+	inherent_verbs = list(/mob/living/carbon/human/proc/darkness_eyes, /mob/living/proc/devour)
+
+	allowed_eat_types = TYPE_ORGANIC | TYPE_HUMANOID
+
+	gluttonous = TRUE
 
 /datum/species/zombie/handle_post_spawn(var/mob/living/carbon/human/H)
 	H.mutations.Add(CLUMSY)

code/modules/mob/living/carbon/human/species/species_attack.dm

@@ -154,6 +154,10 @@
 
 /datum/unarmed_attack/bite/infectious/apply_effects(var/mob/living/carbon/human/user,var/mob/living/carbon/human/target,var/armour,var/attack_damage,var/zone)
 	..()
+	if(target && target.stat == DEAD)
+		return
+	if(target.internal_organs_by_name["zombie"])
+		to_chat(user, "<span class='danger'>You feel that \the [target] has been already infected!</span>")
 	if(prob(25))
 		if(target.reagents)
 			target.reagents.add_reagent("trioxin", 10)