QAbstractItemModel::supportedDragActions( ) should be called with a list of indexes and the mime data

When a model accepts multiple mime types, but each exclusively on a subtree for the mime type, there is no chance to tell the view that a subtree only accepts one of the mime types and not all.

If QAbstractItemModel::supportedDragActions() was called with a list of indexes and the mime data, the model could decide if the item accepts the given mime data.