glib-sharp will only get a new release with the new API that we need for
3.0 in a year or something. Instead of waiting a year before we can release
something we now have our own internal copy of glib-sharp trunk that will
be dropped once glib-sharp 3.0 is released.
Everything is now compilable and working without any additional patches.
As C# interfaces don't allow a default implementation we
add a static Gst.PresetDefault class that provides static
methods for calling the default GstPreset method implementations.
