QScrollArea::sizeHint() implementation broken

In 5.2, the `viewportSizeHint()` method was added to make it easier to get the size hint of the scroll viewport. In `QAbstractScrollArea::sizeHint()` this is used to set the size hint for the widget when `AdjustToContents` is set as the size adjust policy.

However, QScrollArea overrides this method with one that has nothing at all to do with the viewport. From what I can tell, it seems like `QScrollArea::sizeHint()` should just be deleted so the default implementation can be used, since it seems more correct.

Further, `AdjustToContents` does not work because the internal widget is not watched for size changes, so the geometry is not updated when it should be.