Fix build on OpenBSD's mips architectures.

--- CPU/run.c.orig	Sat Jan  9 06:22:52 2010
+++ CPU/run.c	Mon Aug 20 16:55:19 2012
@@ -31,7 +31,7 @@
 */
 
 
-#ifdef mips
+#if defined(mips) && !defined(__OpenBSD__)
 #define _IEEE 1
 #include <nan.h>
 #else