LuaVoxelManip: Fix minor bug with set_lighting, remove coordinate params for light and liquid updates
Two new configuration options are added: - "enable_ipv6" to enable/disable the overall use of IPv6 - "ipv6_server" to enable/disable the use of IPv6 sockets when running a server (when "enable_ipv6" is enabled)
The previous code did not work when the list did not start at index 0 of the inventory list (issue #779).
The 50 ms delay causes frequent test failures on certain systems with slow network stacks, these failures go away with the 100 ms variant.
