Instead of bailing out if the channel list is incorrect check config
node attributes and default settings first.
Being there also fix flawed LOG messages.
Fixes#1794.
Sometimes, the play position in stream is behind the out stream, mostly
because of timing issue. In this case, the mixer will produce invalid
packets which in return will lead to looping on an invalid packet in
the audio_drv.
Issue #1666.
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082
