Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC r228099:
- Create links to the xz and lzma versions even if BSD grep is not the
default. Nor GNU nor liblzma in base provides such functionality so
it may be useful.

MFC r228319:
- Match GNU behavior of exit code
- Rename variable that has a different meaning now

MFC r226664:
- Install BSD grep properly, based on the value of WITH_BSD_GREP

Approved by: re (kib)

MFC r226432, r226273:
- Use getprogname() instead of __progname
- Allow disabling bzip2 support with WITHOUT_BZIP2
- Fix handling patterns that start with a dot
- Remove superfluous semicolon
- Fix counting of match limit (-m)

Approved by: re (kib), delphij (mentor, implicit)

MFC 226035, 226047:

Update BSD grep to the latest development version. It has some code
backported that was written for the TRE integration project in Google
Summer of Code 2011. This is a temporary solution until the whole
regex library is not replaced so that BSD grep development can continue
and the backported code gets some review and testing. This change only
improves scalability slightly, there is no big performance boost yet
but several minor bugs have been found and fixed.

Approved by: re (kib), delphij (mentor, implicit)
Sposored by: Google Summer of Code 2011

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Remove redundant assignments to WARNS.

For these directories, WARNS is already implied to be 6.

Build and install a BSD licensed grep.
If WITH_BSD_GREP is not set, it will be 'bsdgrep' and GNUgrep will be
'[ef]grep'. Otherwise, BSD-grep will be the grep family, and GNUgrep
will be 'gnugrep'.

Discussed with: brooks

- Adjust a comment to actual behaviour
- Makefile nit
- Add more CVS/SVN keywords to make it easier to track changes from NetBSD
in case they add further improvements

Approved by: delphij (mentor)
Obtained from: The NetBSD Project

Add BSD grep to the base system and make it our default grep.

Deliverables: Small and clean code (1,4 KSLOC vs GNU's 8,5 KSLOC),
lower memory usage than GNU grep, GNU compatibility,
BSD license.

TODO: Performance is somewhat behind GNU grep but it is only
significant for bigger searches. The reason is complex, the
most important factor is that GNU grep uses lots of
optimizations to improve the speed of the regex library.
First, we need a modern regex library (practically by adopting
TRE), add support for GNU-style non-standard regexes and then
reevalute the performance issues and look for bottlenecks. In
the meantime, for those, who need better performance, it is
possible to build GNU grep by setting WITH_GNU_GREP.

Approved by: delphij (mentor)
Obtained from: OpenBSD (http://www.openbsd.org/cgi-bin/cvsweb/src/usr.bin/grep/),
freegrep (http://github.com/howardjp/freegrep)
Sponsored by: Google SoC 2008
Portbuild tests run by: kris, pav, erwin
Acknowledgements to: fjoe (as SoC 2008 mentor),
everyone who helped in reviewing and testing