Use typedef XDR from <rpc/xdr.h>

__rpc_xdr is no longer available on FreeBSD 10.
(XDR is typedef'd as "struct XDR" and not "struct __rpc_xdr").

By the way, why did we ever need this? Probably
it should be removed. Leaving for __OpenBSD__ for now.

cde/lib/tt/lib/util/tt_xdr_utils.C

@@ -40,7 +40,7 @@
 #include <memory.h>
 #include "tt_options.h"
 
-#if defined(CSRG_BASED)
+#if defined(__OpenBSD__)
 #define XDR __rpc_xdr
 #endif