implemented IKEv2 force_encap connection parameter

enforces UDP encapsulation by faking NAT detection payloads
  to hurdle restrictive firewalls

src/stroke/stroke.c

@@ -110,6 +110,7 @@ static int add_connection(char *name,
 	msg.add_conn.eap_type = 0;
 	msg.add_conn.mode = 1;
 	msg.add_conn.mobike = 1;
+	msg.add_conn.force_encap = 0;
 	
 	msg.add_conn.rekey.reauth = 0;
 	msg.add_conn.rekey.ipsec_lifetime = 0;