Textures: Update permafrost to new dirt, improve stones, add stones side

mods/default/README.txt

@@ -116,6 +116,7 @@ paramat (CC BY-SA 3.0):
   default_emergent_jungle_sapling.png
   default_permafrost.png -- Derived from a texture by Neuromancer (CC BY-SA 3.0)
   default_stones.png -- Derived from a texture by sofar (CC0 1.0)
+  default_stones_side.png -- Derived from a texture by sofar (CC0 1.0)
   default_moss.png
   default_moss_side.png
   default_fence_rail_acacia_wood

mods/default/nodes.lua

@@ -508,7 +508,8 @@ minetest.register_node("default:permafrost", {
 minetest.register_node("default:permafrost_with_stones", {
 	description = "Permafrost with Stones",
 	tiles = {"default_permafrost.png^default_stones.png",
-		"default_permafrost.png"},
+		"default_permafrost.png",
+		"default_permafrost.png^default_stones_side.png"},
 	groups = {cracky = 3},
 	drop = "default:permafrost",
 	sounds = default.node_sound_gravel_defaults(),