Minor mask tweaks, adds alt_head mask refitting, adds fitted versions of unathi masks for the new alt head.

The alt_head mask refitting system works like this: If the player has an alt_head that's not "None", the system will look for an icon state in the most relevant mask icon file that has the mask's icon state and alt_head suffix ("[wear_mask.icon_state]_[alternate_head.suffix]") and, if it exists ([(alternate_head && ("[wear_mask.icon_state]_[alternate_head.suffix]" in mask_icon.IconStates())) ? "_[alternate_head.suffix]" : ""]") the mask sprite that will appear on the character will have that icon state. If it doesn't exist, the mask sprite that will appear on the character will have the default icon state for the mask object.

code/modules/mob/living/carbon/human/appearance.dm

@@ -133,6 +133,8 @@
 			update_markings()
 
 	update_body(1, 1) //Update the body and force limb icon regeneration to update the head with the new icon.
+	if(wear_mask)
+		update_inv_wear_mask()
 	return 1
 
 /mob/living/carbon/human/proc/reset_hair()

code/modules/mob/living/carbon/human/update_icons.dm

@@ -1013,13 +1013,21 @@ var/global/list/damage_icon_parts = list()
 		if(inv)
 			inv.update_icon()
 	if(wear_mask && (istype(wear_mask, /obj/item/clothing/mask) || istype(wear_mask, /obj/item/clothing/accessory)))
+		var/obj/item/organ/external/head/head_organ = get_organ("head")
+		var/datum/sprite_accessory/alt_heads/alternate_head
+		if(head_organ.alt_head && head_organ.alt_head != "None")
+			alternate_head = alt_heads_list[head_organ.alt_head]
+
 		var/image/standing
+		var/icon/mask_icon = new(wear_mask.icon)
 		if(wear_mask.icon_override)
-			standing = image("icon" = wear_mask.icon_override, "icon_state" = "[wear_mask.icon_state]")
+			mask_icon = new(wear_mask.icon_override)
+			standing = image("icon" = wear_mask.icon_override, "icon_state" = "[wear_mask.icon_state][(alternate_head && ("[wear_mask.icon_state]_[alternate_head.suffix]" in mask_icon.IconStates())) ? "_[alternate_head.suffix]" : ""]")
 		else if(wear_mask.sprite_sheets && wear_mask.sprite_sheets[species.name])
-			standing = image("icon" = wear_mask.sprite_sheets[species.name], "icon_state" = "[wear_mask.icon_state]")
+			mask_icon = new(wear_mask.sprite_sheets[species.name])
+			standing = image("icon" = wear_mask.sprite_sheets[species.name], "icon_state" = "[wear_mask.icon_state][(alternate_head && ("[wear_mask.icon_state]_[alternate_head.suffix]" in mask_icon.IconStates())) ? "_[alternate_head.suffix]" : ""]")
 		else
-			standing = image("icon" = 'icons/mob/mask.dmi', "icon_state" = "[wear_mask.icon_state]")
+			standing = image("icon" = 'icons/mob/mask.dmi', "icon_state" = "[wear_mask.icon_state][(alternate_head && ("[wear_mask.icon_state]_[alternate_head.suffix]" in mask_icon.IconStates())) ? "_[alternate_head.suffix]" : ""]")
 
 		if(!istype(wear_mask, /obj/item/clothing/mask/cigarette) && wear_mask.blood_DNA)
 			var/image/bloodsies = image("icon" = species.blood_mask, "icon_state" = "maskblood")
@@ -1292,13 +1300,15 @@ var/global/list/damage_icon_parts = list()
 			icon_path = "[copytext(icon_path, 1, findtext(icon_path, "/suit.dmi"))]/collar.dmi" //If this file doesn't exist, the end result is that COLLAR_LAYER will be unchanged (empty).
 			if(fexists(icon_path)) //Just ensuring the nonexistance of a file with the above path won't cause a runtime.
 				var/icon/icon_file = new(icon_path)
-				standing = image("icon" = icon_file, "icon_state" = "[wear_suit.icon_state]")
+				if(wear_suit.icon_state in icon_file.IconStates())
+					standing = image("icon" = icon_file, "icon_state" = "[wear_suit.icon_state]")
 		else if(wear_suit.sprite_sheets && wear_suit.sprite_sheets[species.name])
 			var/icon_path = "[wear_suit.sprite_sheets[species.name]]"
 			icon_path = "[copytext(icon_path, 1, findtext(icon_path, "/suit.dmi"))]/collar.dmi" //If this file doesn't exist, the end result is that COLLAR_LAYER will be unchanged (empty).
 			if(fexists(icon_path)) //Just ensuring the nonexistance of a file with the above path won't cause a runtime.
 				var/icon/icon_file = new(icon_path)
-				standing = image("icon" = icon_file, "icon_state" = "[wear_suit.icon_state]")
+				if(wear_suit.icon_state in icon_file.IconStates())
+					standing = image("icon" = icon_file, "icon_state" = "[wear_suit.icon_state]")
 		else
 			if(wear_suit.icon_state in C.IconStates())
 				standing = image("icon" = C, "icon_state" = "[wear_suit.icon_state]")

code/modules/mob/new_player/sprite_accessories.dm

@@ -2349,6 +2349,7 @@
 	icon = null
 	icon_state = null
 	species_allowed = null
+	var/suffix = null
 
 /datum/sprite_accessory/alt_heads/none
 	name = "None"
@@ -2360,3 +2361,4 @@
 	name = "Unathi Sharp Snout"
 	species_allowed = list("Unathi")
 	icon_state = "head_sharp"
+	suffix = "sharp"