swift234

Implement Clang module's "getTopLevelDecls" using the Swift lookup tables.

Various interface-printing facilities use getTopLevelDecls to
enumerate the top-level declarations of a given module. For modules
imported from Clang, this walked a giant cached list of all
declarations known from Clang, then filtered out those that didn't
fit. Instead, just use the information provided by the Swift name
lookup tables, which is inherently module-specific and complete.