C++: fix 'using' in separate block of scope

Task-number: QTCREATORBUG-12357
Change-Id: I7397b0e66783d3249daa5a8ee422bfd5f5bc7bea
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>

src/libs/cplusplus/LookupContext.h

@@ -328,7 +328,7 @@ public:
     }
 
 private:
-    QList<LookupItem> lookupByUsing(const Name *name, Scope *scope) const;
+    QList<LookupItem> lookupByUsing(const Name *name, ClassOrNamespace *bindingScope) const;
 
     // The current expression.
     Document::Ptr _expressionDocument;