Default: Add bush stem and leaves nodes

To allow mapgen bushes in green-grass and savanna grasslands.
Nodes for a generic bush and an acacia bush.
Stem nodes are craftable to a single wood node to provide a small
amount of wood resource in grasslands.
Fuel times are that of corresponding 'wood' nodes, 1/4 that of
corresponding tree nodes.
No leafdecay to enable use as hedges or without a nearby tree trunk.
Uses 'default leaves simple' texture for extra visual thickness.

mods/default/nodes.lua

@@ -131,6 +131,11 @@ default:dry_grass_3
 default:dry_grass_4
 default:dry_grass_5
 
+default:bush_stem
+default:bush_leaves
+default:acacia_bush_stem
+default:acacia_bush_leaves
+
 Corals
 ------
 
@@ -1216,6 +1221,55 @@ for i = 2, 5 do
 end
 
 
+minetest.register_node("default:bush_stem", {
+	description = "Bush Stem",
+	drawtype = "plantlike",
+	visual_scale = 1.18,
+	tiles = {"default_bush_stem.png"},
+	inventory_image = "default_bush_stem.png",
+	wield_image = "default_bush_stem.png",
+	paramtype = "light",
+	sunlight_propagates = true,
+	groups = {choppy = 2, oddly_breakable_by_hand = 1, flammable = 2},
+	sounds = default.node_sound_wood_defaults(),
+})
+
+minetest.register_node("default:bush_leaves", {
+	description = "Bush Leaves",
+	drawtype = "allfaces_optional",
+	waving = 1,
+	visual_scale = 1.3,
+	tiles = {"default_leaves_simple.png"},
+	paramtype = "light",
+	groups = {snappy = 3, flammable = 2, leaves = 1},
+	sounds = default.node_sound_leaves_defaults(),
+})
+
+minetest.register_node("default:acacia_bush_stem", {
+	description = "Acacia Bush Stem",
+	drawtype = "plantlike",
+	visual_scale = 1.18,
+	tiles = {"default_acacia_bush_stem.png"},
+	inventory_image = "default_acacia_bush_stem.png",
+	wield_image = "default_acacia_bush_stem.png",
+	paramtype = "light",
+	sunlight_propagates = true,
+	groups = {choppy = 2, oddly_breakable_by_hand = 1, flammable = 2},
+	sounds = default.node_sound_wood_defaults(),
+})
+
+minetest.register_node("default:acacia_bush_leaves", {
+	description = "Acacia Bush Leaves",
+	drawtype = "allfaces_optional",
+	waving = 1,
+	visual_scale = 1.3,
+	tiles = {"default_acacia_leaves.png"},
+	paramtype = "light",
+	groups = {snappy = 3, flammable = 2, leaves = 1},
+	sounds = default.node_sound_leaves_defaults(),
+})
+
+
 --
 -- Corals
 --