Add back spare fields consumed in r237545. It seems that these should only

be consumed to maintain backward compatibility in stable, but should not be
consumed in head.

Submitted by:	trasz, attilio (indirectly)

sys/geom/geom.h

@@ -110,6 +110,7 @@ struct g_class {
 	g_ioctl_t		*ioctl;
 	g_provgone_t		*providergone;
 	g_resize_t		*resize;
+	void			*spare1;
 	void			*spare2;
 	/*
 	 * The remaining elements are private
@@ -142,6 +143,7 @@ struct g_geom {
 	g_ioctl_t		*ioctl;
 	g_provgone_t		*providergone;
 	g_resize_t		*resize;
+	void			*spare0;
 	void			*spare1;
 	void			*softc;
 	unsigned		flags;