First seemingly working attack making maximal_flushable_txn_set implemented.
Fixed some trivial bug with began_waiting_for_flush_ check in maximal_flushable_txn_set (sigh).
Added comments in maximal_flushable_txn_set.
Removed the unused function exists_flushable_txn_set.
Made remove_txn_set_from_graph not fallaciously try to find a newly flushable txn set.
Replaced extraneous std::set use with std::vector for our precious outer loop performance.
Added if (!poisoned) around the marked_not subseqer case in the cache.
Merge branch 'sam_multiple_index_writes' into sam_multiple_iii_better
Adjusted comment.