MacOS provides an older version of bison which results in
macro redifinitions for CMSG_LEN and CMSG_DATA. Renaming
them resolves this.

Still missing: An implementation of is_thread_sleeping() for MacOS.

MacOS uses a different name for the TCP_INFO socket option.

Use the portable pcap_set_immediate_mode() function instead of
BIOCIMMEDIATE.

Thanks to Timo Voelker for finding and reporting the bug.

When using TFO and the SYN carries user data, the sending of
the SYN-ACK is delayed and accept returns. This allows the
application to provide user data to be put in the SYN-ACK.

Use the IANA assigned option number for the TCP Fast Open option.
Use EXP-FO instead of TO for using the deprecate experimental option.