Added new unit test, fragments 6 -> 4.
Also test some "big fragments" 4 -> 6.
bugfix in skb_init_cb_ipv6, read packect.c for more information.
skb_print improved to print the payload (read it I cant explain it :P)
bugfix for translate_packet, I found this because of the "big fragments", if the first skb_ipv4 is fragmented, the next fragments created by jool were lost.