user32: Load version for comctl32 v6 window classes.
So that versioned window classes gets registered as well. Otherwise, comctl32 v6 fails to register
its window classes when comctl32 v5 classes are still being used. This can happen, for example, when
creating a window using comctl32 v5, then unload comctl32 v5 and not destroying the window, and then
load comctl32 v6.