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

diff --git a/coreutils/date.c b/coreutils/date.c
index d2d77f4..57c826a 100644
--- a/coreutils/date.c
+++ b/coreutils/date.c
@@ -10,7 +10,7 @@
  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */
 
-#include "busybox.h"
+#include "libbb.h"
 
 /* This 'date' command supports only 2 time setting formats,
    all the GNU strftime stuff (its in libc, lets use it),