Log Message:
Update to 2.16. From the changelog:

[CONFUSING BEHAVIOR & UPCOMING CHANGES]
The -w has a confusing behavior that it's had since back to ack 1.x
that will be changing in the future.  It's not changing in this
version, but this is a heads-up that it's coming.

ack -w is "match a whole word", and ack does this by putting turning
your PATTERN into \bPATTERN\b.  So "ack -w foo" effectively becomes
"ack \bfoo\b".  Handy.

The problem is that ack doesn't put a \b before PATTERN if it begins
with a non-word character, and won't put a \b after PATTERN if it
ends with a non-word character.

The problem is that if you're searching for "fool" or "foot", but
only as a word, and you do "ack -w foo[lt]" or "ack -w \ 
(fool|foot)",
you'll get matches for "football and foolish" which certainly should
not match if you're using -w.

[ENHANCEMENTS]
Include .cljs, .cljc and .edn files with the --clojure filetype.  Thanks,
Austin Chamberlin.

Added .xsd to the --xml filetype.  Thanks, Nick Morrott.

Added support for Swift language.  Thanks, Nikolaj Schumacher. (GH #512)

The MSYS2 project is now seen as Windows.  Thanks, Ray Donnelly. (GH #450)

Expand the definition of OCaml files.  Thanks, Marek Kubica. (GH #511)

Add support for Groovy Server Pages.  Thanks, Ethan Mallove. (GH #469)

The JSP filetype (--jsp) now recognizes .jspf files.  Thanks, Sebastien
Feugere.  (GH #586)

Many optimizations and code cleanups.  Thanks, Stephan Hohe.

Added --hpp option for C++ header files.  Thankis, Steffen Jaeckel.

ack now supports --ignore-dir=match:....  Thanks, Ailin Nemui! (GitHub ticket #42)

ack also supports --ignore-dir=ext:..., and --noignore-dir supports match/ext as well

[INTERNALS]
Added test to test --output. Thanks, Varadinsky! (GH #587, GH #590)

Added test to make sure subdirs of target subdirs are ignored if
--ignore-dir applies to them.  Thanks, Pete Houston. (GH #570)

[DOCUMENTATION]
Expanded the explanation of how the -w flag works.  Thanks, Ed Avis.
(GH #585)

[FIXES]
Reverted an optimization to make \s work properly again. (GH #572,
GH #571, GH #562, GH #491, GH #498)

Fixed an out-of-date FAQ entry.  Thanks, Jakub Wilk.  (GH #580)

The -l and -c flags would sometimes return inaccurate results due to
a bug introduced in 2.14.  Thanks to Elliot Shank for the report! (GH #491)

Behavior when using newlines in a search was inconsistent.  Thanks to
Yves Chevallier for the report! (GH #522)

Add minimal requirement of Getopt::Long 2.38, not 2.35, for GetOptionsFromString.

Don't ignore directories that are specified as command line targets (GH #524)

Fix a bug where a regular expression that matches the empty string could cause ack
to go into an infinite loop (GH #542)