Symlinks are not extracted

[rominf]

Steps to reproduce

$ cd /tmp
$ ln -s broken_symlink_destination broken_symlink
$ tar -czvf broken_symlink.tar.gz broken_symlink
$ echo -e 'import nimarchive\n\nextract("/tmp/broken_symlink.tar.gz", "/tmp/output")' >/tmp/test_nimarchive_broken_symlink.nim
$ nim run /tmp/test_nimarchive_broken_symlink.nim
# No broken_symlink in /tmp/output