Changes to “Priority rounds, empty blocks and the previous producer”

+ The producer of block N stays in the draw for block N+1, but its draws count as no earlier than round 10, the last round that may carry transactions. Its block weight is capped the same way: in the weight formula its draw count *k* is never less than 10, so if it does make block N+1 as the fallback, the block adds at most a tenth of the weight of a first-round block (see [[fork-choice]]). In practice another drawn node makes block N+1 whenever one is able to.