swift234

[SE-0033] Add _SwiftNewtypeWrapper protocol for swift_newtype'd types.

This protocol lets us identify swift_newtype'd types. More
importantly, use protocol extensions to make it easy to transfer
specific conformances from the underlying type to the wrapper
type. So, for example, if the underlying type is Hashable, make the
wrapper type Hashable as well. Do the same for Equatable, Comparable,
and _ObjectiveCBridgeable. Fixes rdar://problem/26010804.