[regression] Mac tab key "Text boxes and lists only" vs "All controls" setting is not respected in Qt5

In OSX, there is a setting at System Preferences -> Keyboard -> Keyboard Shortcuts where the Tab key can be configured either to tab between "All controls" or between "Text boxes and lists only". This is stored as the AppleKeyboardUIMode setting. The default value (on OSX 10.7 at least) is "Test boxes and lists only".

In Qt 4.8, Qt would read this setting and obey the behavior, so Qt apps would behave the same as native Mac apps.

In Qt 5, the code for doing this seems to have been removed, meaning that Qt always behaves as if "All controls" is set. Compare initialization of qt_tab_all_widgets variable between Qt 4 and Qt 5.

The tst_QApplication::focusChanged autotest attempts to test this behavior, so it is currently failing on mac (unless the user has set "All controls").