RIST main profile RTP section

This branch provides the next step of the RIST specification. This is the RTP extensions from the main profile. Three is one extension to "compress" null MPEG-TS packets into a bitfield to reduce bandwidth. The other one is RTP sequence number extensions to extend them with an extra 16 bits.

What is not included in this branch is putting this extension into the jitterbuffer and actually allowing it to have more than 64k packets long. This will be in another MR later.

gst/rist/gstrist.h

@@ -50,10 +50,18 @@ GType gst_rist_src_get_type (void);
 
 #define GST_TYPE_RIST_SINK          (gst_rist_sink_get_type())
 #define GST_RIST_SINK(obj)          (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_RIST_SINK,GstRistSink))
-typedef struct _GstRistSink GstRistSink; 
+typedef struct _GstRistSink GstRistSink;
 typedef struct {
   GstBinClass parent;
 } GstRistSinkClass;
 GType gst_rist_sink_get_type (void);
 
+#define GST_TYPE_RIST_RTP_EXT      (gst_rist_rtp_ext_get_type())
+#define GST_RIST_RTP_EXT(obj)      (G_TYPE_CHECK_INSTANCE_CAST((obj),GST_TYPE_RIST_RTP_EXT,GstRistRtpExt))
+typedef struct _GstRistRtpExt GstRistRtpExt;
+typedef struct {
+  GstElementClass parent;
+} GstRistRtpExtClass;
+GType gst_rist_rtp_ext_get_type (void);
+
 #endif