swift234

StdlibUnittest: Fix NSException catching (broken by SE-0054).

Previously, the callback for objc_setUncaughtExceptionHandler
took a parameter of type 'AnyObject!', which was implicitly
unwrapped at all uses inside the closure. When that became
'AnyObject?', we started getting an extra layer of Optional in
the printed output.

This reverts the tests to their pre-4d540c2a state.