Don't use malloc.h header on OpenBSD.

--- src/round_cap.c.orig	Wed Nov 19 22:59:05 2014
+++ src/round_cap.c	Wed Nov 19 22:59:10 2014
@@ -12,7 +12,6 @@
  */
 
 
-#include <malloc.h>
 #include <stdlib.h>
 #include <math.h>
 #include <string.h>	/* for the memcpy() subroutine */