Add Advanced Docking System library

This library is a fork of the following repository
https://github.com/githubuser0xFFFF/Qt-Advanced-Docking-System
Development started from the following commit
1de42a9766134eecd2611c2b4e209d3e0ede74d2
Incorporate all commits until
3ffbbfb6d01ff211d8349027221a19b1419296b5

 - Rename variables and files to follow the Qt style guide
 - General code cleanup (remove goto, fix typos, add overrides, remove
   explicit slots specifier, replace string-based with functor-based
   connections, replace dynamic_cast with qobject_cast)
 - Replace most preprocessor instructions Q_OS_LINUX/Q_OS_MACOS with
   Utils::HostOsInfo
 - Remove all QT_VERSION preprocessor instructions below 5.11
 - Change loading and storage of workspaces. Store workspaces in
   separate file instead of a list in the Settings.ini
 - Add workspace dialog, model and view for managing workspaces
 - Rename XML tags and use enum/bool instead of ascii art/numbers as
   attribute values. Use base64 instead of hex for storing geometry info
 - Remove internal style sheets
 - Add more build systems (qmake, qbs)
 - Adapt copyright header
 - Remove unix specific build rules
 - Replace ADS_PRINT with QLoggingCategory
 - Replace Java-style with STL-style iterators

Change-Id: Icf8c2fbaccec9680df83c6e2100e3446a090a437
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/libs/advanceddockingsystem/iconprovider.cpp

@@ -0,0 +1,81 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 Uwe Kindler
+** 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 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 (at your option) any later version.
+** The licenses are as published by the Free Software Foundation
+** and appearing in the file LICENSE.LGPLv21 included in the packaging
+** of this file. Please review the following information to ensure
+** the GNU Lesser General Public License version 2.1 requirements
+** will be met: https://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 or (at your option) any later version
+** approved by the KDE Free Qt Foundation. The licenses are as published by
+** the Free Software Foundation and appearing in the file LICENSE.GPL3
+** 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.
+**
+****************************************************************************/
+
+#include "iconprovider.h"
+
+#include <QVector>
+
+namespace ADS {
+    /**
+     * Private data class (pimpl)
+     */
+    struct IconProviderPrivate
+    {
+        IconProvider *q;
+        QVector<QIcon> m_userIcons{IconCount, QIcon()};
+
+        /**
+         * Private data constructor
+         */
+        IconProviderPrivate(IconProvider *parent);
+    };
+    // struct LedArrayPanelPrivate
+
+    IconProviderPrivate::IconProviderPrivate(IconProvider *parent)
+        : q(parent)
+    {}
+
+    IconProvider::IconProvider()
+        : d(new IconProviderPrivate(this))
+    {}
+
+    IconProvider::~IconProvider()
+    {
+        delete d;
+    }
+
+    QIcon IconProvider::customIcon(eIcon iconId) const
+    {
+        Q_ASSERT(iconId < d->m_userIcons.size());
+        return d->m_userIcons[iconId];
+    }
+
+    void IconProvider::registerCustomIcon(eIcon iconId, const QIcon &icon)
+    {
+        Q_ASSERT(iconId < d->m_userIcons.size());
+        d->m_userIcons[iconId] = icon;
+    }
+
+} // namespace ADS