display-gst: Use Playbin for GStreamer 1.9.0 onwards
display-gst: Use Playbin for GStreamer 1.9.0 onwards

The Playbin can provide the full pipeline which reduces the
overall maintenance in the code as we don't need to track which
decoder can work with our stream type.

We need to maintain the GstCaps per SPICE_VIDEO_CODEC_TYPE in order to
tell Playbin the type of data we expect. This much should be covered
by spice-protocol and very likely we will need to extend it in the
future to allow more settings that might not possible to verify at
runtime.

This patch keeps previous code for compatibility reasons.

Note that we have to wait Playbin to emit "source-setup" in order to
configure GstAppSrc with the capabilities of input stream. If in the
unlikely event of frames arriving while GstAppSrc is not setup, we
will drop those frames.

Signed-off-by: Victor Toso <39b7599ff73bbf5db531748ba5250f21fa7120ff@redhat.com>
Acked-by: Pavel Grunt <fbda40b445316123f12a5a6bd7556918ea74f4bc@redhat.com>

flexVDI/spice-gtk,flexVDI/spice-gtk