[PyQt] PyQt5 5.11.2 regression: Missing QAbstractItemModel.VerticalSortHint

[Ales Erjavec]

Hi,

The `QAbstractItemModel` is missing the VerticalSortHint and other
members of the `LayoutChangeHint` at the class namespace level.

```
from PyQt5.QtCore import QAbstractItemModel
h = QAbstractItemModel.VerticalSortHint
```
raises a "AttributeError: type object 'QAbstractItemModel' has no
attribute 'VerticalSortHint'"
Works as expected on 5.10.1 and 5.9.2

Tested on macOS, PyQt5 5.11.2  installed from wheels.

Best wishes
    Aleš Erjavec