Making range changefeeds work.
Making `.orderby.between.limit.changes` work (plus bugfix).
Made `.between.orderby.limit.changes` inital value read work correctly.
Removed dead code.
Made `limit_order_t` less dangerous.
Moved around arguments to `on_mod_report`.
Added THROWS_NOTHING specificiers.
Merge branch 'mlucy_range_changefeeds' into next
Merge branch 'v1.15.x' into next
Merge branch 'next' into sam_fix_build