Clean up base-library structure

This patch moves the base library from src/base to src/lib/base,
flattens the library-internal directory structure, and moves the common
parts of the library-description files to base/lib/mk/base.inc and
base/lib/mk/base-common.inc.

Furthermore, the patch fixes a few cosmetic issues (whitespace and
comments only) that I encountered while browsing the result.

Fixes #1952

repos/base-nova/src/lib/base/sleep.cc

@@ -0,0 +1,37 @@
+/*
+ * \brief  Lay back and relax
+ * \author Norman Feske
+ * \author Christian Helmuth
+ * \date   2006-07-19
+ */
+
+/*
+ * Copyright (C) 2006-2016 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.
+ */
+
+/* Genode includes */
+#include <base/sleep.h>
+#include <base/lock.h>
+
+/* base-internal includes */
+#include <base/internal/native_thread.h>
+
+/* NOVA includes */
+#include <nova/syscalls.h>
+#include <nova/util.h>
+
+void Genode::sleep_forever()
+{
+	using namespace Nova;
+
+	Thread_base *myself = Thread_base::myself();
+	addr_t sem = myself ? myself->native_thread().exc_pt_sel + SM_SEL_EC : SM_SEL_EC;
+
+	while (1) {
+		if (Nova::sm_ctrl(sem, SEMAPHORE_DOWNZERO))
+			nova_die();
+	}
+}