sys/sunaudio/: Add a SunAudio source plugin.

sys/sunaudio/: Add a SunAudio source plugin.

Original commit message from CVS:
Patch by: Brian Cameron <brian dot cameron at sun dot com>
* sys/sunaudio/Makefile.am:
* sys/sunaudio/gstsunaudio.c: (plugin_init):
* sys/sunaudio/gstsunaudiomixerctrl.c:
(gst_sunaudiomixer_ctrl_build_list), (gst_sunaudiomixer_ctrl_new),
(gst_sunaudiomixer_ctrl_list_tracks),
(gst_sunaudiomixer_ctrl_get_volume),
(gst_sunaudiomixer_ctrl_set_volume),
(gst_sunaudiomixer_ctrl_set_mute),
(gst_sunaudiomixer_ctrl_set_record):
* sys/sunaudio/gstsunaudiomixerctrl.h:
* sys/sunaudio/gstsunaudiomixertrack.c:
(gst_sunaudiomixer_track_init), (gst_sunaudiomixer_track_new):
* sys/sunaudio/gstsunaudiomixertrack.h:
* sys/sunaudio/gstsunaudiosrc.c: (gst_sunaudiosrc_dispose),
(gst_sunaudiosrc_base_init), (gst_sunaudiosrc_class_init),
(gst_sunaudiosrc_init), (gst_sunaudiosrc_set_property),
(gst_sunaudiosrc_get_property), (gst_sunaudiosrc_getcaps),
(gst_sunaudiosrc_open), (gst_sunaudiosrc_close),
(gst_sunaudiosrc_prepare), (gst_sunaudiosrc_unprepare),
(gst_sunaudiosrc_read), (gst_sunaudiosrc_delay),
(gst_sunaudiosrc_reset):
* sys/sunaudio/gstsunaudiosrc.h:
Add a SunAudio source plugin.
Support stereo and right/left channel gain in the mixer plugin.
Support the RECORD flag so that you can switch between line-input and
microphone in gnome-volume-control.
Code cleanups like using an enumerator for track number instead of an
integer. Fixes #344923.