Added some RSI and RSP comments.
Merge branch 'sam_spinupcluster' into sam_1998
Gave test_txn_t a recency parameter.
Merge branch 'sam_tptest' into sam_1998
Merge branch 'next' into sam_1998
Removed RSI saying to check something (it was checked).
Added and made use of last_write_acquirer_ and last_write_acquirer_version_ in current_page_t.
Removed a stray set_recency_for_block_id call.
Removed unused field current_page_t::cp_block_version_ (formerly current_page_t::block_version_).
Removed the current_page_t::last_modifier_ field and its vestigial connect_preceder logic.
Removed a set_recency_for_block_id call that, apparently, has no reason to exist.
Gave current_page_t::mark_deleted an assertion that there are no subsequent acquirers for this deleted block.
Removed RSI about set_recency_for_block_id callers.
Added assertion when setting last_write_acquirer_ to NULL.
Deduped some code with make_non_deleted.
Merge branch 'next' into sam_1998_backsummary
In page_txn_t::remove_acquirer, removed check for read_cond_.is_pulsed().

We want to treat all write acquirers as having touched the page,
so that subsequent readers do not see recency values that never
make it to disk.
Made serializer_file_write_stream_t use repli_timestamp_t::distant_past.
Merge branch 'next' into sam_1998_backsummary
Merge branch 'next' into sam_1998_backsummary