swift234

[swift_newtype] Handle un-audited CF types

Special case logic for CF types, which may be coming in as
unmanaged. In this case, we will use audit information if present to
import with the new type, otherwise we have to fall back to
Unmanaged<CF...>.

We still import global variables that must be unmanaged onto the new
type, though they keep their unmanaged types. This helps to
consolidate the definitions, as well as make future migration easier
if they get audited.

Test cases included.