omxil: rpi: Fetch pixel aspect ratio from decoder.

The broadcom omx implementation has a vendor extension to fetch pixel aspect
information from the decoder. Use this to pass proper aspect information with
the pictures.

Signed-off-by: Julian Scheel <julian@jusst.de>
decoder: Let decoder modules set dpb size.

As many decoder modules do manage their dpb completely internal and do not
benefit from a picture buffer large enough to hold the dpb in VLC itself, let
the decoders decide about the required dpb size.
As of now the only decoder utilizing the dpb through the VLC picture_buffer is
libmpeg2, which is adapted to announce it's actual dpb size.

Signed-off-by: Julian Scheel <julian@jusst.de>
omxil: Activate direct rendering mode.

Allow the omx core to use direct rendering.

Signed-off-by: Julian Scheel <julian@jusst.de>
wip: Increase number of omx buffers for direct rendering.

To activate direct rendering the vlc core requires enough buffers to store the
dpb (makes not much sense with omx...) and the internally kept references. For
mpeg2 this is 14. Hence increase the buffercount to 14 for testing.

This is not meant to go mainline like this!
wip: Timing hack for OMX on rpi.

No clue why we need this atm, will hopefully drop it soon.