Don't use malloc.h header on OpenBSD.

--- src/fitness.c.orig	Thu Nov 20 01:46:34 2014
+++ src/fitness.c	Thu Nov 20 01:46:49 2014
@@ -1,5 +1,4 @@
 #include <assert.h>
-#include <malloc.h>
 #include <stdio.h>
 
 #include "fitness.h"
