closedcaption: implement and use a helper CCBuffer object for dealing with buffering closed caption data

commit 35f65aae

cccombiner: initial implementation of using CCBuffer helper

commit 213f7908

closedcaption: move CC buffering to helper object

Move most of the interesting code from ccconverter to this new helper
object.

commit 74271430

closedcaption: move cdp->cc_data into shared location

So it can be used by both ccconverter and cccombiner

commit 534e6da6

closedcaption: move cc_data->cdp to shared file

Used by both ccconverter and cccombiner

commit c96376fa

ccconverter: avoid different indent versions indenting !! differently.

commit 67ffc1ea

closedcaption: move cdp framerate table to common file

shared by both cccombiner and ccconverter

commit 0116fb5c

cccombiner: don't assume a single cea608 data packet per buffer

e.g. 24fps can have up to 3 and would include either two field0 or
field1 cea608 data.

commit e1ad87cf

ccconverter: drop data when overflow on extracting cea608 from cc_data

If the buffer overflows, then drop rather than causing a failure and
fropping the output buffer indefinitely.  This may have caused downstream to
be waiting for data the will never arrive.

commit 11deb951

ccconverter: fix framerate passthrough with malformed input

If an input is malformed (only produces cea608 field 1 cc_data) then
when in passthrough we would effectively be dropping every second cea608
on output as we would not store any unused cea608 data.

Fix by having all code paths go through the framerate conversion code
which will store and retrieve any relevant data across buffers.