Yesterday, I simplified how we stream top-level decls.

After a discussion with Ted, we both came to the conclusion that adding a "HandleTopLevelDeclaration" hook to ASConsumer is far more elegant. The default implementation of HandleTopLevelDeclaration will be responsible for iterating over the ScopedDecl (which has a chain of the decls:-).

TODO: Once Ted adds HandleTopLevelDeclaration, make sure TagDecls are chainged appropriately...
llvm-svn: 44445