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

diff --git a/shell/ash.c b/shell/ash.c
index ed46e1c..b1d22e5 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -53,7 +53,7 @@
 #if DEBUG
 #define _GNU_SOURCE
 #endif
-#include "busybox.h"
+#include "busybox.h" /* for struct bb_applet */
 #include <paths.h>
 #include <setjmp.h>
 #include <fnmatch.h>