- fixed a bug where a retransmitted TCP ACK segment did not contain the
ACK flag
[sys net sixlowpan]
- changed sixlowpan architecture: IPV6 packets now always get stored in
sixlowpan (reassembly) buffer and are transmitted one after the other
(FIFO) to IPV6 layer via a separate transfer thread
- fixed a bug where a retransmit of a payload tcp_hc packet did not have
the payload added because total_sent_bytes wasnt reset to 0 after last
transmit