This avoids conflics with definitions on Solaris 10.4.

Remove the inclusion of netinet/sctp.h after enabling SCTP support
in platfroms.h.

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.