SourceCodeClassifier marks unused open declarations

![image](https://cloud.githubusercontent.com/assets/873919/3530402/235c77fe-07a4-11e4-92f4-95802ae5e057.png)

I will add tests but it basically works. 
For consistency, please put two calls into different lines. We should avoid verbose syntax as much as possible. This comment applies for similar uses of `;` in `walk*` functions.