Cavegen: Respect is_ground_content MapNode setting; fix some code formatting issues
Fixed potential NULL pointer and leak when setting node metadata
LuaVoxelManip: Add get_light_data() and set_light_data()
LuaVoxelManip: Add area parameters back to calc_lighting and set_lighting, made optional this time; also fixed a slight bug with night values being ignored
Change default value of is_ground_content to true

Most modders would otherwise forget to explicitly define this, and generated nodes aliased from mods would wall-off caves
Merge remote-tracking branch 'minetest/master'

Conflicts:
	src/mapnode.cpp