Move repositories to 'repos/' subdirectory

This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.

Issue #1082

repos/base/src/core/version.cc

@@ -0,0 +1,14 @@
+/*
+ * \brief  Provide version informaion (core-only)
+ * \author Christian Helmuth
+ * \date   2014-04-11
+ */
+
+/*
+ * Copyright (C) 2014 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.
+ */
+
+namespace Genode { char const *version_string = GENODE_VERSION; }