Add the drivers listed in audio_possible_drivers to audio_drv_list,
using the try-* variants.  That way the probable drivers are compiled by
default if possible.

Additioal tweaks:
  linux: reorder to: pa alsa sdl oss.
  *bsd: drop pa.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20190124112055.547-7-kraxel@redhat.com