add sleep & date, thanks kamil

sleep.c

@@ -0,0 +1,18 @@
+/* See LICENSE file for copyright and license details. */
+#include <stdlib.h>
+#include <unistd.h>
+#include "util.h"
+
+int
+main(int argc, char *argv[])
+{
+	unsigned int seconds;
+
+	if(argc != 2)
+		eprintf("usage: %s seconds\n", argv[0]);
+
+	seconds = atoi(argv[1]);
+	while((seconds = sleep(seconds)) > 0)
+		;
+	return EXIT_SUCCESS;
+}