swift234

Implement support for non-verbatim T[] -> AnyObject[] upcasts.

One of my recent type-checker changes starting passing all array
upcasts, including "bridged" ones like String[] -> AnyObject[],
through the library entry point _arrayUpCast, which is only meant for
class/ObjC existential types that are bridged verbatim.

Fixes part of <rdar://problem/16952238>; more cleanup to follow.

Swift SVN r18283