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.