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/clangtool.h

@@ -44,7 +44,7 @@ class ClangTool : public QObject
 
 public:
     ClangTool(const QString &name);
-    virtual ~ClangTool();
+    ~ClangTool() override;
 
     virtual void startTool(bool askUserForFileSelection) = 0;