Patch from Larry Doolittle (with minor touchups from me so everything compiles

and works) to use the applet definitions in applets.h to autogenerate the applet
function and usage prototypes.

applets/busybox.c

@@ -3,6 +3,10 @@
 #include <stdio.h>
 #include <string.h>
 #include <errno.h>
+
+#undef APPLET
+#undef APPLET_NOUSAGE
+#undef PROTOTYPES
 #include "applets.h"
 
 #define bb_need_full_version