Integrate SIGNAL session into PD session

This patch removes the SIGNAL service from core and moves its
functionality to the PD session. Furthermore, it unifies the PD service
implementation and terminology across the various base platforms.

Issue #1841

repos/base/include/signal_source/client.h

@@ -0,0 +1,30 @@
+/*
+ * \brief  Client-side signal-source interface
+ * \author Norman Feske
+ * \date   2016-01-04
+ */
+
+/*
+ * Copyright (C) 2016 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__SIGNAL_SOURCE__CLIENT_H_
+#define _INCLUDE__SIGNAL_SOURCE__CLIENT_H_
+
+#include <base/rpc_client.h>
+#include <pd_session/pd_session.h>
+
+namespace Genode { class Signal_source_client; }
+
+struct Genode::Signal_source_client : Rpc_client<Signal_source>
+{
+	Signal_source_client(Capability<Signal_source> signal_source)
+	: Rpc_client<Signal_source>(signal_source) { }
+
+	Signal wait_for_signal() override { return call<Rpc_wait_for_signal>(); }
+};
+
+#endif /* _INCLUDE__SIGNAL_SOURCE__CLIENT_H_ */