Ports new zmimic changes/bugfixes/etc from Bay/Nebula. (#14495)

code/modules/lighting/lighting_overlay.dm

@@ -122,14 +122,6 @@
 				0, 0, 0, 1
 			)
 
-	// If we're on an openturf, update the shadower object too.
-	if (T.above)
-		var/turf/simulated/open/OT = T.above
-		if (OT.shadower)
-			OT.shadower.copy_lighting(src)
-		else
-			OT.update_icon()
-
 #undef ALL_EQUAL
 
 // Variety of overrides so the overlays don't get affected by weird things.

code/modules/lighting/lighting_source.dm

@@ -394,7 +394,7 @@
 		// Note: above is defined on ALL turfs, but below is only defined on OPEN TURFS.
 
 		// Upwards lights are handled at the corner level, so only search down.
-		if (T && (T.flags & MIMIC_BELOW) && T.below)
+		if (T && (T.z_flags & ZM_MIMIC_BELOW) && T.below)
 			T = T.below
 			goto check_t
 

code/modules/lighting/lighting_source_sunlight.dm

@@ -99,7 +99,7 @@
 		CHECK_TICK
 
 		// Sunlight only checks downwards as it has no need to shine upwards, really.
-		if (T && (T.flags & MIMIC_BELOW) && T.below)
+		if (T && (T.z_flags & ZM_MIMIC_BELOW) && T.below)
 			T = T.below
 			goto check_t