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.
These audio drivers enable support for Intel HD Audio (Azalia) and
Ensoniq AudioPCI (ES1370) compatible soundcards. They are ported
from OpenBSD 5.7.
Fixes#1498.