CPlusPlus: CppEditor: refactor overview model

Introduce abstract model to be able to use clang
based version of it in follow up patches.
Fix warnings and modernize source code a little.
Move OverviewModel to CppTools.

Change-Id: Idcc9bf03cad047026a456bd01063597a1eb95147
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/plugins/cpptools/cppoverviewmodel.h

@@ -0,0 +1,65 @@
+/****************************************************************************
+**
+** 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
+
+#include "abstractoverviewmodel.h"
+
+#include <cplusplus/CppDocument.h>
+#include <cplusplus/Overview.h>
+
+namespace CppTools {
+
+class CPPTOOLS_EXPORT OverviewModel : public AbstractOverviewModel
+{
+    Q_OBJECT
+
+public:
+    OverviewModel(QObject *parent = nullptr);
+    ~OverviewModel() override;
+
+    QModelIndex index(int row, int column,
+                      const QModelIndex &parent = QModelIndex()) const override;
+    QModelIndex parent(const QModelIndex &child) const override;
+    int rowCount(const QModelIndex &parent = QModelIndex()) const override;
+    int columnCount(const QModelIndex &parent = QModelIndex()) const override;
+    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override;
+
+    CPlusPlus::Document::Ptr document() const override;
+    CPlusPlus::Symbol *symbolFromIndex(const QModelIndex &index) const override;
+
+    void rebuild(CPlusPlus::Document::Ptr doc) override;
+
+private:
+    bool hasDocument() const;
+    unsigned globalSymbolCount() const;
+    CPlusPlus::Symbol *globalSymbolAt(unsigned index) const;
+
+private:
+    CPlusPlus::Document::Ptr _cppDocument;
+    CPlusPlus::Overview _overview;
+};
+
+} // namespace CppTools