Update checking feature (#2648)

* Check on startup (toggleable setting) and manually
* Option to check for pre-releases (eg, 2.4.0-beta1)
* Only included if WITH_XC_NETWORKING is enabled

tests/TestUpdateCheck.h

@@ -0,0 +1,32 @@
+/*
+ *  Copyright (C) 2019 KeePassXC Team <team@keepassxc.org>
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 2 or (at your option)
+ *  version 3 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef KEEPASSX_TESTUPDATECHECK_H
+#define KEEPASSX_TESTUPDATECHECK_H
+
+#include <QObject>
+
+class TestUpdateCheck : public QObject
+{
+Q_OBJECT
+
+private slots:
+    void initTestCase();
+    void testCompareVersion();
+};
+
+#endif // #define KEEPASSX_TESTUPDATECHECK_H