Revert "get rid of mob.see_in_dark and species.darksight"

This reverts commit 278a4c38ec.

code/modules/mob/dead/observer/observer.dm

@@ -34,6 +34,7 @@ var/global/list/image/ghost_sightless_images = list() //this is a list of images
 /mob/dead/observer/New(mob/body)
 	sight |= SEE_TURFS | SEE_MOBS | SEE_OBJS | SEE_SELF
 	see_invisible = SEE_INVISIBLE_OBSERVER
+	see_in_dark = 100
 	verbs += /mob/dead/observer/proc/dead_tele
 
 	stat = DEAD
@@ -634,12 +635,10 @@ This is the proc mobs get to turn into a ghost. Forked from ghostize due to comp
 /mob/dead/observer/proc/updateghostsight()
 	if (!seedarkness)
 		see_invisible = SEE_INVISIBLE_OBSERVER_NOLIGHTING
-		see_in_dark = 100
 	else
 		see_invisible = SEE_INVISIBLE_OBSERVER
 		if (!ghostvision)
 			see_invisible = SEE_INVISIBLE_LIVING;
-		see_in_dark = 0
 	updateghostimages()
 
 /proc/updateallghostimages()