tt_xdr_utils.h: fix build error on linux/bsd introduced with illumos initial patch.

The linux's and BSD's need the 'struct XDR::xdr_ops ops' declaration,
whereas I guess sun does not.

cde/lib/tt/lib/util/tt_xdr_utils.h

@@ -55,7 +55,11 @@ class _Tt_xdr_size_stream : public _Tt_allocated {
 #ifdef __DECCXX
         XDR::xdr_ops ops;
 #else
+# if defined(sun)
 	struct xdr_ops ops;
+# else
+	struct XDR::xdr_ops ops;
+# endif
 #endif
 };