The mixer is not directly necessary for the avplay demo. But it implies
additional maintenance work. E.g., in the current state, it complains about
the missing Report server and mutes audio output by default.
Ref #1910
With the introducation of the Audio_in session interface it makes
sense to rename the current available audio drivers. At the moment
only the dde_bsd audio_drv supports Audio_out as well as Audio_in.
The Linux audio_drv only supports Audio_out (there is no demand for
Audio_in support currently) but is renamed nonetheless to make it
easiert to write generic run scripts.
Issue #1644.
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
