Gave both current_page_t and page_t block_id fields.
Added consider_evicting_current_page, not used anywhere.  current_page_t::can_be_evicted returns false.
Renamed can_be_evicted to should_be_evicted.
Implemented current_page_t::should_be_evicted and added read_ahead_cb_ check to page_cache_t::consider_evicting_current_page, but the function is still unused.
Merge branch 'next' into sam_2137
Added other applicable uses of calling consider_evicting_current_page.
Made consider_evicting_current_page not fill in the sparse holes in the segmented vector, just out of general principle.
Removed RSI comment about read-ahead ending.
Fixed RSI comment about current_page_t::block_id_.
Added the other appropriate calls to consider_evicting_current_page.
Merge branch 'next' into sam_2137
Merge branch 'next' into sam_2137
Removed consider_evicting_current_page call in page_ptr_t::reset... for now.
Forced the page_ptr_t::reset method it to be used, with an assertion in its destructor.
Improved comment.
Added non-mandatory current_page_t::reset method.
Made the current_page_t::reset method mandatory.
Renamed method to reset_page_ptr.
Made reset_page_ptr and current_page_t::reset take a page_cache_t.
Removed page_cache_t field from page_ptr_t.