swift234

SwiftRemoteMirror: Lower types with imported / Objective-C types

- Lower Objective-C class typerefs as strong references with unknown
reference counting.
- Lower other imported C types as builtin blobs of their known
size, alignment, etc.

In the future, it might be beneficial to track which stored properties
of imported types are pointers, for better conservative scanning of
outgoing pointers to the heap.

rdar://problem/26240258
rdar://problem/26240394