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

old_craft_grid, craft_inv) and
minetest.register_craft_predict(itemstack, player, old_craft_grid,
craft_inv)

This not only makes the vector functions faster, but also makes them more
consistent with other functions.

Add support for parameter 'visual_scale' for drawtypes 'signlike' and 'torchlike' like used for drawtype 'plantlike'

6b927229 Changed the default server step
from 0.05s to 0.1s

Add minetest.get_gametime() API function, that returns the number of seconds since the world was created.