Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

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.

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

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

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>