audit small applets and mark some of them as NOFORK.
Put big scary warnings in relevant places.

diff --git a/coreutils/sleep.c b/coreutils/sleep.c
index b89b0fe..592005b 100644
--- a/coreutils/sleep.c
+++ b/coreutils/sleep.c
@@ -18,12 +18,12 @@
  * time suffixes for seconds, minutes, hours, and days.
  */
 
-#include <stdlib.h>
-#include <limits.h>
-#include <unistd.h>
 #include "busybox.h"
 
-#ifdef CONFIG_FEATURE_FANCY_SLEEP
+/* This is a NOFORK applet. Be very careful! */
+
+
+#if ENABLE_FEATURE_FANCY_SLEEP
 static const struct suffix_mult sfx[] = {
 	{ "s", 1 },
 	{ "m", 60 },
@@ -36,9 +36,9 @@
 int sleep_main(int argc, char **argv);
 int sleep_main(int argc, char **argv)
 {
-	unsigned int duration;
+	unsigned duration;
 
-#ifdef CONFIG_FEATURE_FANCY_SLEEP
+#if ENABLE_FEATURE_FANCY_SLEEP
 
 	if (argc < 2) {
 		bb_show_usage();
@@ -50,7 +50,7 @@
 		duration += xatoul_range_sfx(*argv, 0, UINT_MAX-duration, sfx);
 	} while (*++argv);
 
-#else  /* CONFIG_FEATURE_FANCY_SLEEP */
+#else  /* FEATURE_FANCY_SLEEP */
 
 	if (argc != 2) {
 		bb_show_usage();
@@ -58,7 +58,7 @@
 
 	duration = xatou(argv[1]);
 
-#endif /* CONFIG_FEATURE_FANCY_SLEEP */
+#endif /* FEATURE_FANCY_SLEEP */
 
 	if (sleep(duration)) {
 		bb_perror_nomsg_and_die();