MFC r317254: bsdgrep: add BSD_GREP_FASTMATCH knob for built-in fastmatch

Bugs have been found in the fastmatch implementation as used in bsdgrep.
Some have been fixed (r316495) while fixes for others are in review
(D10098).

In comparison with the fastmatch implementation, Kyle Evans found that:

- regex(3)'s performance with literal expressions offers a speed
  improvement over fastmatch

- regex(3)'s performance, both with simple BREs and EREs, seems to be
  comparable

The regex implementation was imported in r226035, and the commit message
reports:

    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.

Introduce a WITH_/WITHOUT_BSD_GREP_FASTMATCH knob to support testing
of both approaches.

Regenerate src.conf(5) as per the original commit

PR:		175314, 194823
Approved by:	emaste (mentor, blanket MFC)

1 files changed, 6 insertions, 1 deletions

diff --git a/share/man/man5/src.conf.5 b/share/man/man5/src.conf.5
index c71a7d7..5d5571c 100644
--- a/share/man/man5/src.conf.5
+++ b/share/man/man5/src.conf.5
@@ -1,6 +1,6 @@
 .\" DO NOT EDIT-- this file is generated by tools/build/options/makeman.
 .\" $FreeBSD$
-.Dd August 5, 2017
+.Dd August 16, 2017
 .Dt SRC.CONF 5
 .Os
 .Sh NAME
@@ -214,6 +214,11 @@ Set to not build the BSD licensed version of cpio based on
 .Xr libarchive 3 .
 .It Va WITH_BSD_GREP
 Install BSD-licensed grep as '[ef]grep' instead of GNU grep.
+.It Va WITHOUT_BSD_GREP_FASTMATCH
+Set this option to exclude the fastmatch implementation from
+.Xr bsdgrep 1 ,
+instead using only
+.Xr regex 3 .
 .It Va WITHOUT_BSNMP
 Set to not build or install
 .Xr bsnmpd 1