Fix warning:

libavformat/nut.c: In function ‘ff_nut_free_sp’:
libavformat/nut.c:80: warning: passing argument 4 of ‘av_tree_enumerate’ from incompatible pointer type
./libavutil/tree.h:92: note: expected ‘int (*)(void *, void *)’ but argument is of type ‘void (*)(void *, void *)’

Originally committed as revision 22659 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/nut.c

@@ -69,9 +69,10 @@ void ff_nut_add_sp(NUTContext *nut, int64_t pos, int64_t back_ptr, int64_t ts){
     }
 }
 
-static void enu_free(void *opaque, void *elem)
+static int enu_free(void *opaque, void *elem)
 {
     av_free(elem);
+    return 0;
 }
 
 void ff_nut_free_sp(NUTContext *nut)