Add marram grass for coastal sand dunes

Use noise with 1 octave and flag 'absvalue' to create sand paths
in dunes.

mods/default/nodes.lua

@@ -147,6 +147,10 @@ default:fern_1
 default:fern_2
 default:fern_3
 
+default:marram_grass_1
+default:marram_grass_2
+default:marram_grass_3
+
 default:bush_stem
 default:bush_leaves
 default:bush_sapling
@@ -1373,6 +1377,57 @@ for i = 2, 3 do
 end
 
 
+minetest.register_node("default:marram_grass_1", {
+	description = "Marram Grass",
+	drawtype = "plantlike",
+	waving = 1,
+	tiles = {"default_marram_grass_1.png"},
+	inventory_image = "default_marram_grass_1.png",
+	wield_image = "default_marram_grass_1.png",
+	paramtype = "light",
+	sunlight_propagates = true,
+	walkable = false,
+	buildable_to = true,
+	groups = {snappy = 3, flammable = 3, attached_node = 1},
+	sounds = default.node_sound_leaves_defaults(),
+	selection_box = {
+		type = "fixed",
+		fixed = {-6 / 16, -0.5, -6 / 16, 6 / 16, -0.25, 6 / 16},
+	},
+
+	on_place = function(itemstack, placer, pointed_thing)
+		-- place a random marram grass node
+		local stack = ItemStack("default:marram_grass_" .. math.random(1, 3))
+		local ret = minetest.item_place(stack, placer, pointed_thing)
+		return ItemStack("default:marram_grass_1 " ..
+			itemstack:get_count() - (1 - ret:get_count()))
+	end,
+})
+
+for i = 2, 3 do
+	minetest.register_node("default:marram_grass_" .. i, {
+		description = "Marram Grass",
+		drawtype = "plantlike",
+		waving = 1,
+		tiles = {"default_marram_grass_" .. i .. ".png"},
+		inventory_image = "default_marram_grass_" .. i .. ".png",
+		wield_image = "default_marram_grass_" .. i .. ".png",
+		paramtype = "light",
+		sunlight_propagates = true,
+		walkable = false,
+		buildable_to = true,
+		groups = {snappy = 3, flammable = 3, attached_node = 1,
+			not_in_creative_inventory=1},
+		drop = "default:marram_grass_1",
+		sounds = default.node_sound_leaves_defaults(),
+		selection_box = {
+			type = "fixed",
+			fixed = {-6 / 16, -0.5, -6 / 16, 6 / 16, -0.25, 6 / 16},
+		},
+	})
+end
+
+
 minetest.register_node("default:bush_stem", {
 	description = "Bush Stem",
 	drawtype = "plantlike",