gstevent: Add some FIXME: 2.0 about removing the timestamp
gstevent: Add some FIXME: 2.0 about removing the timestamp

The timestamp field isn't valuable or used well anywhere. We
should remove it for GStreamer 2.0

https://bugzilla.gnome.org/show_bug.cgi?id=761462

StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer