new utilities.

the .C files compile but are renamed to avoid building automatically.

src/cmd/sleep.c

@@ -0,0 +1,13 @@
+#include <u.h>
+#include <libc.h>
+
+void
+main(int argc, char *argv[])
+{
+	long secs;
+
+	if(argc>1)
+		for(secs = atol(argv[1]); secs > 0; secs--)
+			sleep(1000);
+	exits(0);
+}