Clang: Support second translation unit

A TranslationUnit is owned by TranslationUnits now. TranslationUnits
allows to add another TranslationUnit and to update/query the recently
and previously parsed translation unit.

This does not change any behavior yet.

Change-Id: I8a2f0cc05d3e51bf739dd5d7c4da14b54147f3ab
Reviewed-by: David Schulz <david.schulz@qt.io>

src/tools/clangbackend/ipcsource/clangbackend_global.h

@@ -0,0 +1,36 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of Qt Creator.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-3.0.html.
+**
+****************************************************************************/
+
+#pragma once
+
+namespace ClangBackEnd {
+
+enum class PreferredTranslationUnit
+{
+    RecentlyParsed,
+    PreviouslyParsed,
+};
+
+} // namespace ClangBackEnd