This makes it possible to ship the bundle stand-alone. Also
note that CMake will automatically pack the game data for
release builds, but sym-link the game data for debug builds.
Note this means you will only see the parts of planet/ that
are mentioned in OC_C4GROUPS in CMakeList.txt! This is equivalent
to the behaviour of the shipped build, so I don't see this as
a problem.
Peter Wortmann