Cast the pointer to void * before casting it back to struct type * in

STAILQ_LAST.  This quiets a warning from GCC about increased required
alignment for the cast.

Idea from:      cognet

sys/sys/queue.h

@@ -274,7 +274,7 @@ struct {								\
 #define	STAILQ_LAST(head, type, field)					\
 	(STAILQ_EMPTY((head)) ?						\
 		NULL :							\
-	        ((struct type *)					\
+	        ((struct type *)(void *)				\
 		((char *)((head)->stqh_last) - __offsetof(struct type, field))))
 
 #define	STAILQ_NEXT(elm, field)	((elm)->field.stqe_next)