Changed snow nodebox to 'walkable = false'

Allows walking in, and prevents being trapped in, 2 node high spaces.
Simulates player's feet sinking into snow.
Easier jumping up onto nodes with snow.

mods/default/nodes.lua

@@ -422,6 +422,7 @@ minetest.register_node("default:snow", {
 	paramtype = "light",
 	buildable_to = true,
 	floodable = true,
+	walkable = false,
 	drawtype = "nodebox",
 	node_box = {
 		type = "fixed",