Avoid compiler warnings when deserializing to a parameterized type

```
Foo<Bar> foo = gson.fromJson(json, Foo.class);

currently produces compiler warning for unchecked conversion and needs 
@SuppressWarnings("unchecked")

Explore revising gson.fromJson(String json, Class<? super T> classOfT) to get 
rid of this warning.
```

Original issue reported on code.google.com by `inder123` on 5 Oct 2010 at 1:53
