* components/sample/main.c (sample_make_object): Connect to the
	"destroy" signal of the view_frame rather than the sample content
	view object, to avoid a race condition where we might exit before
	the view_frame is fully unreffed and has a chance to clean up.
	components/sample/nautilus-sample-content-view.c
	(nautilus_sample_content_view_destroy): Unref the
	NautilusViewFrame when we are destroyed.

	* libnautilus/nautilus-zoomable.c, libnautilus/ntl-view-frame.c,
	libnautilus/ntl-content-view-frame.c,
	libnautilus/ntl-meta-view-frame.c: Use boilerplate macros for
	get_type method and to invoke parent destroy method.

	* libnautilus/nautilus-zoomable.c, libnautilus/ntl-view-frame.c:
	Unref the interface we query_local_interface for, to avoid holding
	a superfluous ref to ourselves, since we eventually add_interface
	that interface.

	* src/ntl-view.c (nautilus_view_destroy_client): Use
	bonobo_object_unref instead of bonobo_object_destroy.