Comment 5 for bug 355945

There is a new controlobject called ChannelX,passthrough_enabled which toggles the passthrough state. It is default off so there are no preferences needed, but there will need to be some sort of UI required. In my own version I had the vinyl status widget turn blue when passthrough was on, but this patch just enables the behavior. (We should probably open a separate bug to complete the UI for it)