swift234

[Clang importer] Generalize name lookup tables for globals-as-members.

A swift_name attribute on a global declaration can specify a dotted
name (e.g., SomeStruct.member) to map that global into a member of the
(Swift-)named type. Handle this mapping in DeclName parsing, plumb it
through importFullName, and cope with it in the Swift name lookup
tables (tested via the dump) and importing into a Swift DeclContext
(as-yet-untested). Part of SE-0033.