NOVA: make noux_tool_chain happy

Multiple calls to get the dataspace capability on NOVA lead to the situation
that the caller gets each time a new mapping of the same capability at
different indexes.

The client/caller assumes to get every time the very same index, e.g. in
Noux the index is used to look up structures.

Cache the dataspace capability returned via a rm_session for base-nova.

base-nova/include/rm_session/client.h

@@ -0,0 +1,59 @@
+/*
+ * \brief  Client-side region manager session interface
+ * \author Christian Helmuth
+ * \author Alexander Boettcher
+ * \date   2006-07-11
+ */
+
+/*
+ * Copyright (C) 2006-2012 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+#ifndef _INCLUDE__RM_SESSION__CLIENT_H_
+#define _INCLUDE__RM_SESSION__CLIENT_H_
+
+#include <rm_session/capability.h>
+#include <base/rpc_client.h>
+
+namespace Genode {
+
+	struct Rm_session_client : Rpc_client<Rm_session>
+	{
+		Dataspace_capability _rm_ds_cap;
+
+		explicit Rm_session_client(Rm_session_capability session)
+		: Rpc_client<Rm_session>(session) { }
+
+		Local_addr attach(Dataspace_capability ds, size_t size, off_t offset,
+		                  bool use_local_addr, Local_addr local_addr,
+		                  bool executable = false)
+		{
+			return call<Rpc_attach>(ds, size, offset,
+			                        use_local_addr, local_addr,
+			                        executable);
+		}
+
+		void detach(Local_addr local_addr) {
+			call<Rpc_detach>(local_addr); }
+
+		Pager_capability add_client(Thread_capability thread) {
+			return call<Rpc_add_client>(thread); }
+
+		void fault_handler(Signal_context_capability handler) {
+			call<Rpc_fault_handler>(handler); }
+
+		State state() {
+			return call<Rpc_state>(); }
+
+		Dataspace_capability dataspace() {
+			if (!_rm_ds_cap.valid())
+				_rm_ds_cap = call<Rpc_dataspace>();
+			return _rm_ds_cap;
+		}
+	};
+}
+
+#endif /* _INCLUDE__RM_SESSION__CLIENT_H_ */