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/demo/src/lib/mini_c/strlen.cc

@@ -0,0 +1,19 @@
+/*
+ * \brief  Mini C strlen()
+ * \author Christian Helmuth
+ * \date   2008-07-24
+ */
+
+/*
+ * Copyright (C) 2008-2013 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.
+ */
+
+#include <util/string.h>
+
+extern "C" Genode::size_t strlen(const char *s)
+{
+	return Genode::strlen(s);
+}