usage.c: remove reference to busybox.h
*: s/include "busybox.h"/include "libbb.h"

diff --git a/coreutils/diff.c b/coreutils/diff.c
index 09cacbd..f6b045b 100644
--- a/coreutils/diff.c
+++ b/coreutils/diff.c
@@ -12,7 +12,7 @@
  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
  */
 
-#include "busybox.h"
+#include "libbb.h"
 
 #define FSIZE_MAX 32768