[mythtv] update cec support to work with v2 of libcec

[mythtv at phipps-hutton.freeserve.co.uk]

Quoting Karl Dietz <dekarl at spaetfruehstuecken.org>:

> mates, CEC is more then just "yet another input device" (see
> http://en.wikipedia.org/wiki/HDMI#CEC), there nice things like:
> System Standby, OSD Display, Device Menu Control, Routing Control,
> Device OSD Name Transfer or System Audio Control...
>
> Actually I find it more interesting to control TV / amp from MythTV then
> the other way round!

Agreed, there is a lot of potential, but I don't think doing it via  
mythfrontend is going to be simple or happen any time soon. On the  
other hand there is already a branch of libcec-demon that has a socket  
that lets you send arbitrary CEC commands.

Cheers,
Tim.