airfield gfx improvements

- added separate idle shp to allow using all 8 frames while keeping idle/active separate.
- replaced some empty/background pixels inside tower with shadow.

mods/ra/sequences.yaml

@@ -193,24 +193,24 @@ hpad:
 		Length: 6
 
 afld:
-	idle:
-		Start: 4
-		Length: 4
+	idle: afldidle
+		Start: 0
+		Length: 8
 		Tick: 160
-	damaged-idle:
-		Start: 12
-		Length: 4
+	damaged-idle: afldidle
+		Start: 8
+		Length: 8
 		Tick: 160
 	make: afldmake
 		Start: 0
 		Length: *
 	active:
 		Start: 0
-		Length: 4
+		Length: 8
 		Tick: 160
 	damaged-active:
 		Start: 8
-		Length: 4
+		Length: 8
 		Tick: 160
 
 spen: