swift234

[ClangImporter] Handle swift_private renaming for a variety of imported decls.

...including structs and struct fields, enums and enum cases, typedefs,
protocols, classes, and properties.

The main problem is that this /doesn't/ handle top-level /lookup/, so you
can't actually find any of these renamed types. This is fixed in the next
commit.

This does not handle methods, subscripts, or initializers.

Part of rdar://problem/20070465

Swift SVN r29427