[Development] System Locale Update broken

[John Layt]

Hi,

QTBUG-24543 reports that the tst_QLocale::windowsDefaultLocale() test is 
broken and is currently being skipped.

I've determined this is because the Qt4 mechanism for triggering a refresh of 
the Qt system locale whenever the system locale is changed has been removed 
from qapplication_win.cpp and QWindowSystemInterface::handleLocaleChange() in 
Qt5.

Symbian and QNX also support this in Qt4.8 but OSX and Linux do not.

As this is a regression from 4.8 I assume it must be fixed for 5.0, rather 
than just hacking the test to make it pass?  I also assume I need to open a 
separate bug report for it?

The fix I was thinking of is making the QSystemLocale implementations detect 
any change in the system locale and call QLocalePrivate::updateSystemPrivate() 
themselves, which would also emit the QEvent::LocaleChange.

Any thoughts on this?  Any Windows hackers willing to try adapt the old 
qapplication_win.cpp code to fit in qlocale_win.cpp?

John.