[PACKET_HISTORY]: Add dccphtx_rtt and rename the win_count fields

As requested by Ian.

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: Ian McDonald <iam4@cs.waikato.ac.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>