This commits add common elements for Ancillary Data and Closed
Caption support in GStreamer:
* A VBI (Video Blanking Interval) parser that supports detection
and extraction of Ancillary data according to the SMPTE S291M
specification. Currently supports the v210 and UYVY video
formats.
* A new GstMeta for Closed Caption : GstVideoCaptionMeta. This
supports the two types of CC : CEA-608 and CEA-708, along with
the 4 different ways they can be transported (other systems
are super-set of those).
https://bugzilla.gnome.org/show_bug.cgi?id=794901
