Fix dynamic signals on 64 bit architectures
Fix dynamic signals on 64 bit architectures

sizeof(GClosure) is 32 on 64 bit

freedesktop-unofficial-mirror/gstreamer__gstreamer-sharp,gstreamer-sharp/gstreamer-sharp,Forage/gstreamer-sharp,Forage/gstreamer-sharp,Forage/gstreamer-sharp,GStreamer/gstreamer-sharp,GStreamer/gstreamer-sharp,gstreamer-sharp/gstreamer-sharp,Forage/gstreamer-sharp,freedesktop-unofficial-mirror/gstreamer__gstreamer-sharp,freedesktop-unofficial-mirror/gstreamer__gstreamer-sharp,gstreamer-sharp/gstreamer-sharp,GStreamer/gstreamer-sharp