MFC r313695, r313760, r314769, r314863, r314865, r316125

r313695:
MFV r313676: libpcap 1.8.1

r313760:
MFV r313759: license change for a few headers (4 clause BSD to 3 clause BSD).

X-MFC-with: r313695

r314769:
Remove compatibility with old libpcap.

Differential Revision: https://reviews.freebsd.org/D9606

r314863:
Stop installing pcap-int.h, which is the internal interface for libpcap.

Reference: https://github.com/the-tcpdump-group/libpcap/issues/560
PR: 217221

r314865:
Bump __FreeBSD_version for removal of pcap-int.h.

PR: 217221

r316125:
MFV r316124: Fix build when WITHOUT_INET6.

Reported by: Randy Westlund <rwestlun gmail com>

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Add META_MODE support.

Off by default, build behaves normally.
WITH_META_MODE we get auto objdir creation, the ability to
start build from anywhere in the tree.

Still need to add real targets under targets/ to build packages.

Differential Revision: D2796
Reviewed by: brooks imp

Convert usr.sbin to LIBADD
Reduce overlinking

use .Mt to mark up email addresses consistently (part2)

PR: 191174
Submitted by: Franco Fichtner <franco@lastsummer.de>

Update my e-mail to my FreeBSD one.

Approved by: joel (mentor)

Replace index() and rindex() calls with strchr() and strrchr().

The index() and rindex() functions were marked LEGACY in the 2001
revision of POSIX and were subsequently removed from the 2008 revision.
The strchr() and strrchr() functions are part of the C standard.

This makes the source code a lot more consistent, as most of these C
files also call into other str*() routines. In fact, about a dozen
already perform strchr() calls.

The last big commit: let usr.sbin/ use WARNS=6 by default.

Several cleanups to ipfwpcap(8).

- Enable WARNS?=6.
- Include missing headers.
- Mark prog and pidfile as static. Remove unneeded initializer.
- Use ANSI prototypes.
- Remove unneeded fp variable.
- snprintf() guarantees the buffer to be null terminated. Remove
unneeded - 1 and bzero call.
- Remove unneeded casting.

Submitted by: Pawel Worach, Christoph Mallon

Add a signal handler for SIGINT to make sure that the PID file
gets cleaned up upon receiving SIGINT. This un-breaks subsequent
executions of ipfwpcap and helps when debugging network/divert
issues like this:

ipfwpcap -r 6000 - | tcpdump -r -

MFC after: 1 week

Change authors e-mail.

Requested by: Niclas Zeising

Revise markup.

add define's from config.h for pcap-int.h; this is a noop now
but will be required for libpcap 0.9.4

s/packages/packets/

Noticed by: maxim

Add manual page for ipfwpcap(8).

Reviewed by: phk, brueffer
Submitted by: Niclas Zeising <lothrandil@n00b.apagnu.se>

Add a small tool which captures packets on a DIVERT socket and writes
them as pcap (tcpdump) format data to a file or pipe.

Volunters wanted for: manpage
Contributed by: P Kern <pkern@cns.utoronto.ca>