[MIRROR] Adds defines for mouse_opacity (#2381)

* Adds defines for mouse_opacity

* Delete misc.dm.rej

* Update misc.dm

code/modules/atmospherics/environmental/LINDA_fire.dm

@@ -45,7 +45,7 @@
 //This is the icon for fire on turfs, also helps for nurturing small fires until they are full tile
 /obj/effect/hotspot
 	anchored = TRUE
-	mouse_opacity = 0
+	mouse_opacity = MOUSE_OPACITY_TRANSPARENT
 	icon = 'icons/effects/fire.dmi'
 	icon_state = "1"
 	layer = ABOVE_OPEN_TURF_LAYER

code/modules/atmospherics/gasmixtures/gas_types.dm

@@ -95,7 +95,7 @@ GLOBAL_LIST_INIT(hardcoded_gases, list("o2","n2","co2","plasma")) //the main fou
 
 /obj/effect/overlay/gas
 	icon = 'icons/effects/tile_effects.dmi'
-	mouse_opacity = 0
+	mouse_opacity = MOUSE_OPACITY_TRANSPARENT
 	layer = FLY_LAYER
 	appearance_flags = TILE_BOUND