insertbin: mark as unstable API

gst-libs/gst/insertbin/Makefile.am

@@ -48,6 +48,7 @@ GstInsertBin-@GST_API_VERSION@.gir: $(INTROSPECTION_SCANNER) libgstinsertbin-@GS
 		--pkg gstreamer-base-@GST_API_VERSION@ \
 		--pkg-export gstreamer-insertbin-@GST_API_VERSION@ \
 		--add-init-section="gst_init(NULL,NULL);" \
+		-DGST_USE_UNSTABLE_API \
 		--output $@ \
 		$(gir_headers) \
 		$(gir_sources)

gst-libs/gst/insertbin/gstinsertbin.h

@@ -26,6 +26,11 @@
 #ifndef __GST_INSERT_BIN_H__
 #define __GST_INSERT_BIN_H__
 
+#ifndef GST_USE_UNSTABLE_API
+#warning "The GStreamer insertbin library is unstable API and may change in future."
+#warning "You can define GST_USE_UNSTABLE_API to avoid this warning."
+#endif
+
 #include <gst/gst.h>
 
 G_BEGIN_DECLS