Ensure that there is no space before /udp().

This is based on https://github.com/freebsd-net/packetdrill/pull/15
but adds support for af_arg, getsockopt() and clearing the
acceptfilter.

Allow the last parameter of setsockopt() and getsockopt() calls
to be ....

This was suggested in https://github.com/freebsd-net/packetdrill/pull/15
and a partial implementation was provided.

Sync with freebsd-net's version

add support for ignoring tcp sequence number and timestamp offset cha…

In order to simulate delayed packets, there are occasions where responses
to those packets need to be ignored insofar as they modify relative sequence
numbers or timestamps. For example a retransmitted SYN or SYN-ACK might be delayed
until after the TCP session ends, but a combination of bugs on the client and server
might result in the session persisting as if it never ended.

inbound injected packet:  0.100034 S 0:0(0) win 65535 <mss 1460,nop,wscale 6,sackOK,TS val 100 ecr 0>
outbound sniffed packet:  0.100083 S. 3079308609:3079308609(0) ack 1 win 65535 <mss 1460,nop,wscale 4,sackOK,TS val 3206488061 ecr 100>
inbound injected packet:  0.150127 . 1:101(100) ack 3079308610 win 1031 <nop,nop,TS val 150 ecr 3206488061>
outbound sniffed packet:  0.150170 . 3079308610:3079308610(0) ack 101 win 12495 <nop,nop,TS val 3206488111 ecr 150>
outbound sniffed packet:  0.150192 P. 3079308610:3079309010(400) ack 101 win 12501 <nop,nop,TS val 3206488111 ecr 150>
inbound injected packet:  0.200251 . 101:101(0) ack 3079309010 win 1024 <nop,nop,TS val 200 ecr 3206488111>
inbound injected packet:  0.200271 F. 101:101(0) ack 3079309010 win 1031 <nop,nop,TS val 200 ecr 3206488111>
outbound sniffed packet:  0.200287 . 3079309010:3079309010(0) ack 102 win 12501 <nop,nop,TS val 3206488161 ecr 200>
outbound sniffed packet:  0.200324 F. 3079309010:3079309010(0) ack 102 win 12501 <nop,nop,TS val 3206488161 ecr 200>
inbound injected packet:  0.250354 . 102:102(0) ack 3079309011 win 1031 <nop,nop,TS val 250 ecr 3206488161>
inbound injected packet:  0.265380 S 0:0(0) win 65535 <mss 1460,nop,wscale 6,sackOK,TS val 100 ecr 0>
outbound sniffed packet:  0.265402 S. 3079308609:3079308609(0) ack 1 win 65535 <mss 1460,nop,wscale 4,sackOK,TS val 3118763918 ecr 100>
inbound injected packet:  0.300437 . 1:1(0) ack 3079308610 win 1031 <nop,nop,TS val 150 ecr 3206488061>
outbound sniffed packet:  0.300455 R 3079308610:3079308610(0) win 0

 0.000 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+0.000 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+0.000 bind(3, ..., ...) = 0
+0.000 listen(3, 1) = 0
+0.100 < S  0:0(0) win 65535 <mss 1460,nop,wscale 6,sackOK,TS val 100 ecr 0>
+0.000 > S. 0:0(0) ack 1 win 65535 <mss 1460,nop,wscale 4,sackOK,TS val 200 ecr 100>
+0.050 < . 1:101(100) ack 1 win 1031 <nop, nop, TS val 150 ecr 200>
+0.000 accept(3, ..., ...) = 4
+0.000 read(4, ..., 100) = 100
+0.000 write(4, ..., 400) = 400
+0.000 > . 1:1(0) ack 101 win 12495 <nop, nop, TS val 250 ecr 150>
+0.000 > P. 1:401(400) ack 101 win 12501 <nop, nop, TS val 250 ecr 150>
+0.050 < . 101:101(0) ack 401 win 1024 <nop, nop, TS val 200 ecr 250>
+0.000 < F. 101:101(0) ack 401 win 1031 <nop, nop, TS val 200 ecr 250>
+0.000 > . 401:401(0) ack 102 win 12501 <nop, nop, TS val 300 ecr 200>
+0.000 close(4) = 0
+0.000 > F. 401:401(0) ack 102 win 12501 <nop, nop, TS val 300 ecr 200>
+0.050 < . 102:102(0) ack 402 win 1031 <nop, nop, TS val 250 ecr 300>
+0.015 < S  0:0(0) win 65535 <mss 1460,nop,wscale 6,sackOK,TS val 100 ecr 0!>
+0.000 > S. ...(0) ack 1 win 65535 <mss 1460,nop,wscale 4,sackOK,TS val ... ecr 100>
+0.035 < . 1:1(0) ack 1 win 1031 <nop, nop, TS val 150 ecr 200>
+0.000 > . 1:1(0) ack 1 win 12501 <nop, nop, TS val 200 ecr 150>

Fix https://github.com/nplab/packetdrill/issues/131.

Improve interface handling in local mode

On *BSD platforms the original version always used the tun0 device
in local mode and never deleted it, except on NetBSD. This was
handy when using for example Wireshark for capturing trafic.
The last commit removed this possibility, since it removes the
interface. Add the --persistent_tun_dev command line option
to bring it back.

To get the behaviour of the original version, use on *BSD
platforms --tun-dev=tun0 --persistent_tun_dev.

When using local mode on *BSD, using the tun0 device was hard
coded in contrast to Linux, where the next unused tun device
was used.
This patch changes the behaviour on *BSD to use the next unused
tun device. This also requires that the device is removed when
packetdrill terminates. This was the case on Linux, but not on
*BSD.
On *BSD there is also a new command line option (--tun-dev) to
set the device name and not select an ephemerial one.

Get in sync with the nplab version

Sponsored by:	Netlix, Inc.

Sponsored by:	Netflix, Inc.

This allows to support a mixture of encapsulated and non-encapsulated
packets in a single script file.

Sponsored by:	Netflix, Inc.

Ensure sequence numbers are mapped correctly.

This adds support for SCTP/UDP and TCP/UDP including ICMP
support.

Sponsored by:	Netflix, Inc.

Improve debugging

Wrap the run time deubg option in a compile time option. (DEBUG)

Merge gnns changes to make the debug mode run time selectable.