Finish off the log part of _swift_checkClassAndWarnForKeyedArchiving. (#10418)
Finish off the log part of _swift_checkClassAndWarnForKeyedArchiving. (#10418)

Logs a warning the first time a problematic class is archived or
unarchived. We expect people to actually fix these issues, so the
performance of the warning isn't too important.

Sample output:

  [timestamp] Attempting to archive Swift class '_Test.Outer.ArchivedThenUnarchived', which does not have a stable runtime name.
  [timestamp] Use the 'objc' attribute to ensure that the runtime name will not change: "@objc(_TtCC5_Test5Outer22ArchivedThenUnarchived)"
  [timestamp] If there are no existing archives containing this class, you can choose a unique, prefixed name instead: "@objc(ABCArchivedThenUnarchived)"

Finishes rdar://problem/32414508
apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation