[PATCH] v4l: experimental Sliced VBI API support

Adds all defines, ioctls and structs needed for the sliced VBI API

VBI = Vertical Blank Interval.

It is related with the way TV signals work.  It sends a line, then, it has a
retrace time to allow the tube to move electrons to the beginning of the next
line.  This was the main reason at the beginning of analog B&W TV.

There is a lot of bandwidth lost on VBI.  So, lots of TV systems use it to
send other information such as Closed Captions and Teletext.  Also,
broadcasters uses this as a channel to exchange information from the content
producer to their subsidiaries at each city.

There's already a raw VBI interface on V4L2 api, used for Closed Captions and
Teletext.  The decoding is doing at userlevel space and it is mostly for
analog TV signals, non encoded.

Encoded signals (MPEG, for example), may need also to transmit other
information (like, for example, display aspect, i.e.  4x3, widescreen...).
Sliced VBI interface is a method to allow the video stream to transmit this
kind of information.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@brturbo.com.br>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>