plugins/elements/: Use custom marshalers that take GstMiniObject as first parameter.

plugins/elements/: Use custom marshalers that take GstMiniObject as first parameter.

Original commit message from CVS:
* plugins/elements/gstfakesink.c:
(marshal_VOID__MINIOBJECT_OBJECT), (gst_fake_sink_class_init):
* plugins/elements/gstfakesrc.c: (marshal_VOID__MINIOBJECT_OBJECT),
(gst_fake_src_class_init):
Use custom marshalers that take GstMiniObject as first parameter.
Using OBJECT as parameter while a GstMiniObject is given will lead
to assertions if built with G_ENABLE_DEBUG. Fixes bug #525532.