Add libfuzzer test for QTextDocument::setMarkdown()

Change-Id: I729d4a3bb276523011a6f17a800e72aa34540e47
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

tests/libfuzzer/gui/text/qtextdocument/setMarkdown/main.cpp

@@ -0,0 +1,34 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** 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.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QTextDocument>
+
+extern "C" int LLVMFuzzerTestOneInput(const char *Data, size_t Size) {
+    QTextDocument().setMarkdown(QByteArray(Data, Size));
+    return 0;
+}

tests/libfuzzer/gui/text/qtextdocument/setMarkdown/setMarkdown.pro

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+CONFIG += console
+CONFIG -= app_bundle
+SOURCES += main.cpp
+LIBS += -fsanitize=fuzzer