audit small applets and mark some of them as NOFORK.

Put big scary warnings in relevant places.

coreutils/test.c

@@ -21,12 +21,11 @@
  */
 
 #include "busybox.h"
-#include <unistd.h>
-#include <ctype.h>
-#include <errno.h>
-#include <string.h>
 #include <setjmp.h>
 
+/* This is a NOEXEC applet. Be very careful! */
+
+
 /* test(1) accepts the following grammar:
 	oexpr	::= aexpr | aexpr "-o" oexpr ;
 	aexpr	::= nexpr | nexpr "-a" aexpr ;