QLocale - add static function to enable the programmer to add country/language pairs

At the moment there are 2 unespected cases:

• several valid QLocale::Country don't have valid QLocale::Language
• several valid QLocale::Language don't have valid QLocal::Country

So for those it is not possible to create a valid QLocale.

The idea is that the programmer can add pairs to the QLocale so, if needed, it is possible to get a valid QLocale for any valid Country and Language.

This new feature would also set up a matching QLocale::name() for the new QLocale created.