swift234

[g-arc-opts] unchecked_enum_data is always a ref count identity preserving operation, always strip them off.

Originally I was using the notion of layout compatible to define the notion of a
ref count identity preserving operation. This is too restrictive of a definition
since layout compatible implies that the operation does not change the memory
location being pointed at. On the other hand, we just care that the ref counts
are the same.

rdar://18189329

Swift SVN r21613