[widgets] P&C Test suite: default locale

I'm having a go at implementing the defaultlocale attribute, but have a problem with the test cases - these all use defaultlocale="x-w3c-test". 

The problem is that this is a private use code, and so converts to "und-x-w3c-test" during processing. By default I don't even allow BCP extensions in the first place either, and so if I make some exception code just for this language tag its not really a very good test of conformance more generally.

Would it be possible to change the tests to use a real language tag instead?

S