Don't use malloc.h header on OpenBSD.

--- src/ex_raw.c.orig	Wed Nov 19 22:58:14 2014
+++ src/ex_raw.c	Wed Nov 19 22:58:18 2014
@@ -17,7 +17,6 @@
  */
 
 
-#include <malloc.h>
 #include <stdlib.h>
 #include <math.h>
 #include <string.h>	/* for the memcpy() subroutine */