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/crafting.lua

@@ -35,6 +35,20 @@ minetest.register_craft({
 	}
 })
 
+minetest.register_craft({
+	output = 'default:wood',
+	recipe = {
+		{'default:bush_stem'},
+	}
+})
+
+minetest.register_craft({
+	output = 'default:acacia_wood',
+	recipe = {
+		{'default:acacia_bush_stem'},
+	}
+})
+
 minetest.register_craft({
 	output = 'default:stick 4',
 	recipe = {
@@ -929,6 +943,18 @@ minetest.register_craft({
 })
 
 
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:bush_stem",
+	burntime = 7,
+})
+
+minetest.register_craft({
+	type = "fuel",
+	recipe = "default:acacia_bush_stem",
+	burntime = 8,
+})
+
 minetest.register_craft({
 	type = "fuel",
 	recipe = "default:junglegrass",