tcpdump: decode pfsync packets on network interfaces

When print-ip-demux.c was introduced on ee67461e, the pfsync_ip_print
function was missed, causing tcpdump to treat pfsync packets on network
interfaces as an unknown protocol.

MFC after: 1 week
Sponsored by: InnoGames GmbH
Differential Revision: https://reviews.freebsd.org/D42504

tpcdump: Update to 4.99.4

Local changes:

- Update some local modifications to fix build
- Synch config.h with upstream as much as possible

Changelog: https://git.tcpdump.org/tcpdump/blob/55bc126b0216cfe409b8d6bd378f65679d136ddf:/CHANGES
Reviewed by: emaste
Obtained from: https://www.tcpdump.org/release/tcpdump-4.99.4.tar.gz
Sponsored by: The FreeBSD Foundation