Mapgen: Add propagate_shadow bool to calcLighting

To terminate unwanted shadows from floatlands or realms above
Also add to LuaVoxelManip calc_lighting for use in mapgen mods
Remove the 2 argument calcLighting, mapgens now use the 5
argument form to specify the volumes for propagateSunlight and
spreadLight
In mgsinglenode replace calcLighting with setLighting and
clean-up use of tabs and spaces

src/mapgen_singlenode.h

@@ -35,6 +35,7 @@ class MapgenSinglenode : public Mapgen {
 public:
 	u32 flags;
 	content_t c_node;
+	u8 set_light;
 
 	MapgenSinglenode(int mapgenid, MapgenParams *params, EmergeManager *emerge);
 	~MapgenSinglenode();