Don't use malloc.h header on OpenBSD.

--- src/analogue.cpp.orig	Mon Nov  3 22:52:40 2014
+++ src/analogue.cpp	Mon Nov  3 22:52:50 2014
@@ -24,7 +24,6 @@
 
 /*****************************************************************************/
 
-#include <malloc.h>
 #include <math.h>
 #include <stdlib.h>
 #include "cmt.h"