This patch introduces support for using V4L2 VBI devices for
reading NTSC EIA-608 closed captions.

This patch includes feedback from the vlc-devel mailing list from
the Oct 21, 2012, Oct 28, 2012, and Nov 18, 2012 submission attempts.
Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>