ss: add support for bytes_sent, bytes_retrans, dsack_dups and reord_seen

ss: add support for bytes_sent, bytes_retrans, dsack_dups and reord_seen

Wei Wang added these fields in linux-4.19

Tested:

ss -ti ...

	ts sack cubic wscale:8,8 rto:7 rtt:2.678/0.267 mss:1428 pmtu:1500
    rcvmss:536 advmss:1428 cwnd:91 ssthresh:65
(*) bytes_sent:17470606104 bytes_retrans:2856
    bytes_acked:17470483297
    segs_out:12234320 segs_in:622983
    data_segs_out:12234318 send 388.2Mbps lastrcv:986784 lastack:1
    pacing_rate 465.8Mbps delivery_rate 162.7Mbps
    delivered:12234235 delivered_ce:3669056
    busy:986784ms unacked:84 retrans:0/2
(*) dsack_dups:2
    rcv_space:14280 rcv_ssthresh:65535 notsent:2016336 minrtt:0.183

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Wei Wang <weiwan@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Wei Wang <weiwan@google.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>