The Solaris Studio compiler uses different flags...

It seems that -pthread is not really needed...

Add MacOS support

Just using the utun device in combination with libpcap does not
work reliably for IPv6. As a workaround, use pktap,utun.
This also requires to add support DLT_RAW.

MacOS does not support pcap_setdirection() for PCAP_D_OUT.
Instead use only a single pcap handle (as it was originally) and
add a capture filter to only filter the packets in the expected
direction.
Only packets sent by the machine under test needs to be captured.

Although a peer address MUST be specified for IPv4, it MUST NOT
be specified when using IPv6, when configuring the IP address
on an utun device using ifconfig.

This fixes a bug which did not show up on FreeBSD, but on MacOS.

This fixes a bug which did not show up on FreeBSD, but on MacOS.

This requires the tunneling devices to be used in P2P mode. So
pass the gateway address around.
This is not working:
* Can't configure IPv6 addresses on utun devices.
* Can't use libpcap on utun devices
* Can't use libpcap as currently being used (taking the direction
  into account.