Don't use malloc.h header on OpenBSD.

--- src/utility.c.orig	Mon Nov  3 22:18:53 2014
+++ src/utility.c	Mon Nov  3 22:19:46 2014
@@ -44,7 +44,7 @@
 #include <ctype.h>
 #include <libnova/libnova.h>
 
-#ifndef __APPLE__
+#if !defined(__APPLE__) && !defined(__OpenBSD__)
 #include <malloc.h>
 #endif