Fix untar of symlinks. Only hardlinks are relative to top of archive and should be normalized.

Example of tarball with symbolic links:

ftp://ftp.alsa-project.org/pub/lib/alsa-lib-1.1.4.1.tar.bz2

'include/alsa' should point to '.' (that is 'include'). Before fix, it would be an empty directory (not even a symlink).