Split cfeed_artificial_table_backend_t::machinery_t::run into several functions for clarity.
Pass change specs by move.
Fix minor typos and style issues.
Use visitor instead of boost::get to check type of changefeed
Initialize begin_destruction_was_called; catch base_exc_t instead of exc_t.
Use empty ql::datum_t instead of ql::datum_t::null() to indicate insertion and deletion in changefeed msg_t. Also, inline send_all_diffs() into diff_all().
Make repeating_timer_t accept a function callback. Fix artificial table changefeed machinery expiration.
Put THROWS_NOTHING annotation on interruptor.