usage.c: remove reference to busybox.h

*: s/include "busybox.h"/include "libbb.h"

libbb/getopt32.c

@@ -7,8 +7,8 @@
  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
  */
 
-#include "libbb.h"
 #include <getopt.h>
+#include "libbb.h"
 
 /*      Documentation
 

libbb/lineedit.c

@@ -29,7 +29,7 @@
  */
 
 #include <sys/ioctl.h>
-#include "busybox.h"
+#include "libbb.h"
 
 
 /* FIXME: obsolete CONFIG item? */

libbb/selinux_common.c

@@ -4,7 +4,7 @@
  *
  * Copyright 2007 KaiGai Kohei <kaigai@kaigai.gr.jp>
  */
-#include "busybox.h"
+#include "libbb.h"
 #include <selinux/context.h>
 
 context_t set_security_context_component(security_context_t cur_context,

libbb/xfuncs.c

@@ -9,7 +9,7 @@
  * Licensed under GPL version 2, see file LICENSE in this tarball for details.
  */
 
-#include "busybox.h"
+#include "libbb.h"
 
 /* All the functions starting with "x" call bb_error_msg_and_die() if they
  * fail, so callers never need to check for errors.  If it returned, it