We now only allow per port preallocated buffers. We exchange the index
into the array instead of passing the buffers around. We still use the
refcount to track when a buffer can be reused.
Improve API a little, allow passing the node as the first argument of
the interface call.
Implement alloc_buffer in v4l2 and improve the test.
Remove the thread from alsa sink and use the pollfd event.
Make it possible to pass multiple fds in one pollfd event
Add 3 callbacks to the pollfd event and add support for timeouts
