Clang: Rebuild overview model tree when token data is updated

In release builds overview model tree is built earlier
then the job with token information is completed.

Change-Id: I1a563551e813996001fb97924ac441e2b7d599b9
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/cpptools/abstractoverviewmodel.h

@@ -90,6 +90,9 @@ public:
     virtual bool isGenerated(const QModelIndex &) const { return false; }
     virtual Utils::Link linkFromIndex(const QModelIndex &) const = 0;
     virtual Utils::LineColumn lineColumnFromIndex(const QModelIndex &) const = 0;
+
+signals:
+    void needsUpdate();
 };
 
 } // namespace CppTools