SERVER-13635 Kill BSONObjExternalSorter and use Sorter directly
SERVER-13641 Replace InterruptStatus with OperationContext in agg
SERVER-13641 Make agg use OpContext-aware DBDirectClient
SERVER-13641 get OpCtxImpl out of DocSourceCursor
SERVER-13635 Remove Database::_magic
SERVER-13635: add DatabaseCatalogEntry as an interface