[SR-3202] Some of properties of Locale.current object are not filled …

[saiHemak]

…on Linux

[alblue]

@swift-ci please test

[ianpartridge]

Failure caused by GitHub outage.

[pushkarnk]

@swift-ci please test

[pushkarnk]

OK, I get what the problem was.

CFLocaleGetValue called from object(forKey:) always returns AnyObject. Subsequently for the different Locale properties, when we tried to conditionally cast it to a String, a nil was returned (this is what SR-3202 is).

This fix first converts the AnyObject/NSString to String by using _SwiftValue.fetch, due to which a forced downcast in localeIdentifier fails . The second part of the fix removes the forced downcast.

[pushkarnk]

LGTM

@swift-ci please test and merge