mark all virtuals in the clang plugin as override

In order to help catch Clang API changes.

Change-Id: I5738f5dff405f7a2dd377c983fb32c1c7a2ff921

compilerplugins/clang/store/removeforwardstringdecl.hxx

@@ -22,7 +22,7 @@ class RemoveForwardStringDecl
     {
     public:
         explicit RemoveForwardStringDecl( CompilerInstance& compiler, Rewriter& rewriter );
-        virtual void run();
+        virtual void run() override;
         bool VisitNamespaceDecl( const NamespaceDecl* declaration );
     private:
         bool tryRemoveStringForwardDecl( const Decl* decl );