[vala/staging] gstreamer: Update from 1.17.0+ git master

[Rico Tzschichholz <ricotz src gnome org>]

commit 9a28d01cd7f2f17c79c7878306c8f90f5963b29b
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Sun Sep 15 18:04:40 2019 +0200

    gstreamer: Update from 1.17.0+ git master

 vapi/gstreamer-1.0.vapi      | 2 +-
 vapi/gstreamer-base-1.0.vapi | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/vapi/gstreamer-1.0.vapi b/vapi/gstreamer-1.0.vapi
index 55ead7014..53004e922 100644
--- a/vapi/gstreamer-1.0.vapi
+++ b/vapi/gstreamer-1.0.vapi
@@ -1096,7 +1096,7 @@ namespace Gst {
        public abstract class Device : Gst.Object {
                [CCode (has_construct_function = false)]
                protected Device ();
-               public virtual Gst.Element? create_element (string? name);
+               public virtual unowned Gst.Element? create_element (string? name);
                public Gst.Caps? get_caps ();
                public string get_device_class ();
                public string get_display_name ();
diff --git a/vapi/gstreamer-base-1.0.vapi b/vapi/gstreamer-base-1.0.vapi
index 2fe905ea7..2ea72a8e2 100644
--- a/vapi/gstreamer-base-1.0.vapi
+++ b/vapi/gstreamer-base-1.0.vapi
@@ -714,7 +714,7 @@ namespace Gst {
                        public uint get_blocksize ();
                        public Gst.BufferPool get_buffer_pool ();
                        [NoWrapper]
-                       public virtual Gst.Caps get_caps (Gst.Caps filter);
+                       public virtual Gst.Caps get_caps (Gst.Caps? filter);
                        public bool get_do_timestamp ();
                        [NoWrapper]
                        public virtual bool get_size (uint64 size);