add new tcp_info fields from linux v4.6

new fields and associated linux commit:
tcpi_notsent_bytes, tcpi_min_rtt cd9b266095f422267bddbec88f9098b48ea548fc
tcpi_data_segs_in, tcpi_data_segs_out a44d6eacdaf56f74fad699af7f4925a5f5ac0e7f

include/netinet/tcp.h

@@ -184,6 +184,10 @@ struct tcp_info
 	uint64_t tcpi_bytes_received;
 	uint32_t tcpi_segs_out;
 	uint32_t tcpi_segs_in;
+	uint32_t tcpi_notsent_bytes;
+	uint32_t tcpi_min_rtt;
+	uint32_t tcpi_data_segs_in;
+	uint32_t tcpi_data_segs_out;
 };
 
 #define TCP_MD5SIG_MAXKEYLEN    80