ClangTools: Modernize

modernize-use-nullptr
modernize-use-override
modernize-use-equals-default

Change-Id: I14a840c6f2972f57763cdfd4bb4483df1ec261d4
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Marco Bubke <marco.bubke@qt.io>

src/plugins/clangtools/clangtoolsunittests.h

@@ -37,7 +37,7 @@ class ClangToolsUnitTests : public QObject
     Q_OBJECT
 
 public:
-    ClangToolsUnitTests() {}
+    ClangToolsUnitTests() = default;
 
 private slots:
     void initTestCase();