swift234

When force-casting AnyObject to a contextual type, bridge through Objective-C.

Previously, we were relying on user-defined conversions to perform the
final bridging from the Objective-C class type (e.g., NSString) to its
Swift value type (String). That works for NSString <-> String, but not
for arbitrary arrays. Use the bridgeFromObjectiveC() witness instead,
so we can handle:

  let obj: AnyObject = ...
  let strArr: String[] = obj!

Fixes <rdar://problem/16952771>.

Swift SVN r18422