quark 0.24.0: everything that changed

The full notes for this version are its short notes: that was all that was written then.

Ranked mode. Host with RANKED on (Host screen), or run quark_server --ranked. Ranked servers show [RANKED] in the server list.
- Your identity: your game makes a secret key the first time it runs (quark.key, next to quark.cfg). Your rank belongs to that key, so it stays on this computer. Copy the file to take your rank to another PC, and don't share it.
- Reporting: when a ranked match ends, every player's own game sends the result (who played, which side, who placed where) straight to the ranking server. The match is only rated when every player reported exactly the same thing. One different report voids it, and so does a player who never reports within an hour.
- The host is never trusted: it never sees anyone's key, and a lying server just produces reports that don't match. Anyone can host ranked.
- Ratings use OpenSkill (Weng-Lin, Plackett-Luce). It handles 1v1, 2v2, 3v3, uneven teams and free-for-all including ties, and beating stronger players moves you more.
- The rating number is shown as (skill − 3 × uncertainty) × 40, starting at 0. It reads 1234? for your first 5 games while you're still placing.
Where you see it: the scoreboard on ranked servers has a RATING column, and after a match you see how much your rating moved.
Not rated: tourney matches, matches with bots, and matches with more than 16 players (ranked servers don't add bots).
The network protocol changed to version 15, so servers and clients must both be on 0.24.0.