Clarify license of SHA-1 algorithm

SPDX/reuse does not feature any generic 'public domain' license
identifier. So far we claimed CC0, which is however not entirely correct.
Now that we have LICENSES directory, let's correctly claim this as
a specific license.

Also, remove the LGPL in-code claim. The adaptations for Qt code is
minor so it doesn't make much sense to claim a different license.

Pick-to: 6.5
Change-Id: I4e943a45baae192b54c38184e8eb85fc6d4035e5
Reviewed-by: Joerg Bornemann <[email protected]>
Reviewed-by: Volker Hilsheimer <[email protected]>

LICENSES/LicenseRef-SHA1-Public-Domain.txt

@@ -0,0 +1,3 @@
+100% free public domain implementation of the SHA-1 algorithm
+by Dominik Reichl <[email protected]>
+Web: http://www.dominik-reichl.de/

src/3rdparty/sha1/qt_attribution.json

@@ -7,7 +7,7 @@
     "Description": "Implements the Secure Hash Algorithms SHA 1",
     "Homepage": "http://www.dominik-reichl.de/projects/csha1/",
     "License": "Public Domain",
-    "LicenseId": "CC0-1.0",
+    "LicenseId": "LicenseRef-SHA1-Public-Domain",
     "Copyright": "Copyright (C) Dominik Reichl <[email protected]>
 Copyright (C) 2016 The Qt Company Ltd"
 }

src/3rdparty/sha1/sha1.cpp

@@ -1,46 +1,10 @@
-/****************************************************************************
-**
-** Copyright (C) 2016 The Qt Company Ltd.
-** Contact: https://www.qt.io/licensing/
-**
-** This file is part of the Qt Toolkit.
-**
-** $QT_BEGIN_LICENSE:LGPL$
-** 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 3 as published by the Free Software
-** Foundation and appearing in the file LICENSE.LGPL3 included in the
-** packaging of this file. Please review the following information to
-** ensure the GNU Lesser General Public License version 3 requirements
-** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
-**
-** GNU General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU
-** General Public License version 2.0 or (at your option) the GNU General
-** Public license version 3 or 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.GPL2 and 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-2.0.html and
-** https://www.gnu.org/licenses/gpl-3.0.html.
-**
-** $QT_END_LICENSE$
-**
-****************************************************************************/
-
-/*
-  Based on the public domain implementation of the SHA-1 algorithm
-  Copyright (C) Dominik Reichl <[email protected]>
-*/
+// Based on the public domain implementation of the SHA-1 algorithm by Dominik Reichl
+//
+// Copyright (C) Dominik Reichl <[email protected]>
+// Copyright (C) 2016 The Qt Company Ltd.
+//
+// SPDX-License-Identifier: LicenseRef-SHA1-Public-Domain
+
 #include <QtCore/qendian.h>
 
 #ifdef Q_CC_MSVC