* Add GULUserDefaults to GoogleUtilities.
This is a workaround for NSUserDefaults crashing when setting values
in the background in some situations on iOS 11. This uses the C API
in order to avoid an NSNotification firing (which a class eventually
tries to update the UI from the thread that set the value).
* Add missing copyright information.
* Resolve macOS issues, address feedback.
* Removed unnecessary enum value.
