Packets will be discarded if the sending player is not currently
interacting with the appropriate computer. This ensures players cannot
control other people's computers.
This is enforced by checking if the current container is a "computer
container", and this container holds the correct computer.
Updated the source code to the version shipped as the 1.80pr0 alpha
release. Also removed some unnecessary files from the LuaJ subfolder
which were bulking up the repository.