youtube-dl 2014.08.28.2

Closes #31950.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
youtube-dl: update 2014.08.28.2 bottle.
gettext, readline: Add keg_only :shadowed_by_osx
gettext: update 0.19.2 bottle.
readline: update 6.3.6 bottle.