When calling clone(), _data_packet always point to the root of a packet cloning chain/tree instead of the packet on which clone() is called. This allows to kill and effectively free intermediate cloned packets in the chain as described in http://librelist.com/browser//click/2014/11/24/clones-of-clones/ .
Merge pull request #143 from MappaM/parentclone

Keep _data_packet pointing to the original ancestor