Changes:
* `chess.variant.GiveawayBoard` **now starts with castling rights**.
`chess.variant.AntichessBoard` is the same variant without castling rights.
* UCI info parser no longer reports errors when encountering unknown tokens.
* Performance improvements for repetition detection.
* Since Python 3.8: `chess.syzygy`/`chess.polyglot` use `madvise(MADV_RANDOM)`
to prepare table/book files for random access.
Bugfixes:
* Fix syntax error in type annotation of `chess.engine.run_in_background()`.
* Fix castling rights when king is exploded in Atomic. Mitigated by the fact
that the game is over and that it did not affect FEN.
* Fix insufficient material with underpromoted pieces in Crazyhouse. Mitigated
by the fact that affected positions are unreachable in Crazyhouse.
Features:
* Support `wdl` in UCI info (usually activated with `UCI_ShowWDL`).