QTabWidget does not set the selected state on AT-SPI2

The active page_tab in a page_tab_list should have the "selected" state, but in Qt it does not. This can be easily verified by looking at a QTabWidget in Accerciser.

A work-around may be possible by looking for the filler>>(layered_pane, page_tab_list) structure in a Qt application, and assuming the child of the layered_pane with the "showing" state has the same index as the selected tab_page.