$NetBSD$

Fix 64-bit build.

--- runtime/sys.c~	1997-10-16 09:36:19.000000000 -0400
+++ runtime/sys.c	2008-09-04 21:13:32.000000000 -0400
@@ -1,6 +1,7 @@
 /* Basic system calls */
 
 #include <errno.h>
+#include <unistd.h>
 #ifdef __MWERKS__
 #include "myfcntl.h"
 #else
