Don't use malloc.h header on OpenBSD.

--- src/initial.c.orig	Thu Nov 20 01:43:38 2014
+++ src/initial.c	Thu Nov 20 01:43:44 2014
@@ -1,4 +1,3 @@
-#include <malloc.h>
 #include <stdlib.h>
 #include <assert.h>
 
