Cave tileset tweaks & initial winner's path

This adds some RBY elements to the Cave tileset - including some rocks, a button, a sign(!), and the ice tiles. I've modified the rocks so they work with the tileset in-practice, I really liked using these in KEP. I've put together a really really really basic Winner's Path that'll be sorted out one day...

data/tilesets/cave_collision.asm

@@ -62,3 +62,18 @@
 	tilecoll WATER, WATER, WATER, WATER ; 3d
 	tilecoll WATER, WATER, WATER, WATER ; 3e
 	tilecoll FLOOR, FLOOR, PIT, FLOOR ; 3f
+	tilecoll WALL, WALL, WALL, WALL ; 40
+	tilecoll WALL, WALL, WALL, FLOOR ; 41
+	tilecoll WALL, WALL, FLOOR, WALL ; 42
+	tilecoll WALL, FLOOR, WALL, WALL ; 43
+	tilecoll FLOOR, WALL, WALL, WALL ; 44
+	tilecoll WALL, WALL, FLOOR, FLOOR ; 45
+	tilecoll WALL, FLOOR, WALL, FLOOR ; 46
+	tilecoll FLOOR, WALL, FLOOR, WALL ; 47
+	tilecoll FLOOR, FLOOR, WALL, WALL ; 48
+	tilecoll WALL, FLOOR, FLOOR, FLOOR ; 49
+	tilecoll FLOOR, WALL, FLOOR, FLOOR ; 4a
+	tilecoll FLOOR, WALL, FLOOR, FLOOR ; 4b
+	tilecoll FLOOR, FLOOR, WALL, FLOOR ; 4c
+	tilecoll UP_WALL, UP_WALL, FLOOR, FLOOR ; 4d
+	tilecoll UP_WALL, UP_WALL, FLOOR, FLOOR ; 4e