[mac] a Qt app should be able to impose a language to use in native dialogs and strings

Hi

On the mac, the language used within native dialogs and strings (eg : open file dialog, or "preference" string in the menu) is choosen at the system level, based on the user's preferences at the system level.
Cf http://doc.trolltech.com/4.5/mac-differences.html#translating-the-application-menu-and-native-dialogs

There is no mean to impose a given language to use on the native dialogs and strings.

Since a Qt app can choose among the available translations for its *internal* strings, it should be able to choose the corresponding translations for the mac-specific strings as well.

E.G., if only German is available for *internal strings*, then the app should be able to impose German for all the dialogs.

There is to me no interest to have a given language picked for *internal strings*, and another language for the native dialogs, the latest being "controlled at the system level" and not programatically modifiable.

More, this leads to non-coherent application localization.

I suggest:
"at start, an app should be able to get the preferred language at the system level, then choose the best language to use among the available Qt translations, then impose this language throughout the app.
In particular, on the Mac, a Qt app should be able to impose the use of a given language for native dialogs and strings".

This bug relates to QTBUG-190
It also relates to Support Case 00075524