swift234

Importer: Synthesize inferred availability for members mirrored from unannotated Obj-C protocols

The importer conjures up "mirrored" member declarations for imported
Obj-C classes that conform to a protocol with members that aren't exposed
in public headers. This commit extends our existing inference of availability
for members of unannotated Obj-C protocols to cover mirrored declarations
as well. For these mirrored declarations, we additionally constrain the
inferred availability with the availability of the class itself.

Swift SVN r30244