Move Utils::AsynchronousMessageBox to Core::AsynchronousMessageBox

The MainWindow was not always the first window and active has to returned
instead of a nullptr. Using dialogParent should fix it.

Change-Id: If78edb5e9567111aa998bbe5da70b3f148a3fd16
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>

src/plugins/coreplugin/messagebox.h

@@ -0,0 +1,50 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** 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 Digia.  For licensing terms and
+** conditions see http://www.qt.io/licensing.  For further information
+** use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file.  Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+****************************************************************************/
+
+#ifndef MESSAGEBOX_H
+#define MESSAGEBOX_H
+
+#include "core_global.h"
+
+QT_BEGIN_NAMESPACE
+class QString;
+QT_END_NAMESPACE
+
+namespace Core {
+namespace AsynchronousMessageBox {
+
+    CORE_EXPORT void warning(const QString &title, const QString &desciption);
+    CORE_EXPORT void information(const QString &title, const QString &desciption);
+    CORE_EXPORT void critical(const QString &title, const QString &desciption);
+}
+}
+
+#endif // MESSAGEBOX_H
+