ext/pulse/: Implement GstPropertyProbe interface on pulsesink for detecting sink devices and on pulsesrc for detectin...

Original commit message from CVS:
Patch by: Laszlo Pandy <laszlok2 at gmail dot com>
* ext/pulse/pulsesink.c: (gst_pulsesink_interface_supported),
(gst_pulsesink_implements_interface_init),
(gst_pulsesink_init_interfaces), (gst_pulsesink_init),
(gst_pulsesink_finalize), (gst_pulsesink_set_property),
(gst_pulsesink_get_type):
* ext/pulse/pulsesink.h:
* ext/pulse/pulsesrc.c: (gst_pulsesrc_interface_supported),
(gst_pulsesrc_init_interfaces), (gst_pulsesrc_init),
(gst_pulsesrc_finalize), (gst_pulsesrc_set_property):
* ext/pulse/pulsesrc.h:
Implement GstPropertyProbe interface on pulsesink for detecting
sink devices and on pulsesrc for detecting source devices.
Fixes bugs #547227 and #547217.