oggmux: refactor how EOS is determined
This decreases the number of buffers held on each pad by one, eliminating next_buffer. Simplifies the logic by relying solely on CollectPads to let us know when a pad is in EOS. As a side benefit, the collect pads related code is structured more like other CollectPad users. The previous code would occasionally mark the wrong pad as EOS, causing the code to get in a state where all the streams were finished, but EOS hadn't been sent to the source pad.
Showing with 45 additions and 114 deletions