usage.c: remove reference to busybox.h

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

shell/hush.c

@@ -76,12 +76,15 @@
  * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
  */
 
-#include "busybox.h"
+
 #include <glob.h>      /* glob, of course */
 #include <getopt.h>    /* should be pretty obvious */
 /* #include <dmalloc.h> */
+
 extern char **environ; /* This is in <unistd.h>, but protected with __USE_GNU */
 
+#include "busybox.h" /* for struct bb_applet */
+
 
 /* If you comment out one of these below, it will be #defined later
  * to perform debug printfs to stderr: */