ClassCastException on Specific Adapter Cast's

So I ran into a trivial error today, when ListView has to cast the Adapter it cast's it to a BaseAdapter and you implement the interface but it doesn't extend BaseAdapter. This commit is just simply including it.

If you want to see the problem in action try having a listview with enough items for Fast Scrolling to kick in and you'll see the ANR with CastClassException thrown.

Don't forget to enable fast scrolling with

```
android:fastScrollEnabled="true"
```