Merge pull request #13224 from Ghommie/Ghommie-cit835

Removing priority overlays, update_icon() splitup for guns.

code/__DEFINES/subsystems.dm

@@ -146,11 +146,11 @@
 #define SSAIR_EQUALIZE 8
 #define SSAIR_ACTIVETURFS 9
 
+// |= on overlays is not actually guaranteed to not add same appearances but we're optimistically using it anyway.
 #define COMPILE_OVERLAYS(A)\
 	if (TRUE) {\
 		var/list/ad = A.add_overlays;\
 		var/list/rm = A.remove_overlays;\
-		var/list/po = A.priority_overlays;\
 		if(LAZYLEN(rm)){\
 			A.overlays -= rm;\
 			A.remove_overlays = null;\
@@ -159,11 +159,5 @@
 			A.overlays |= ad;\
 			A.add_overlays = null;\
 		}\
-		if(LAZYLEN(po)){\
-			A.overlays |= po;\
-		}\
-		else{\
-			A.priority_overlays = null;\
-		}\
 		A.flags_1 &= ~OVERLAY_QUEUED_1;\
 	}