add gateway subdirectory to source tarball
add gateway subdirectory to source tarball

cvmfs/cvmfs,DrDaveD/cvmfs,DrDaveD/cvmfs,DrDaveD/cvmfs,cvmfs/cvmfs,cvmfs/cvmfs,DrDaveD/cvmfs,cvmfs/cvmfs,cvmfs/cvmfs,DrDaveD/cvmfs,DrDaveD/cvmfs,cvmfs/cvmfs,cvmfs/cvmfs,DrDaveD/cvmfs