Test build: seamless co-op placement (#17) and controller reconnect (#20)

Test build for #17. Not a release: the launcher does not offer it as an update. It is 0.51-linux.13 plus two fixes waiting for testing.

Seamless co-op: a host's placement goes to the sign it rings (#17). BBSC's newer Windows builds changed this, with no source published yet; this build does the same, reimplemented from their DLL, so Linux and updated Windows players understand each other.

• A host ringing a sign sends its placement only to that sign's owner.
• A guest only takes the placement meant for its own sign, so it no longer follows a random host on a busy server, and its sign is advertised where the host that rang it is.
• Placements sent to the whole server by older builds are ignored, as the newer BBSC builds do.

Controller reconnected mid-game (#20). Right after reconnecting, some controllers report every stick at the end of its travel for a moment. That was taken as the stick's resting position, and the camera and the player then spun until the game was restarted. Such readings are now skipped.

What would help:

1. Seamless co-op on Seamless Hunt, with the Linux player as the guest (Kin Bell) and a Windows player on BBSC's latest build hosting (Hunt Bell). Then the other way round.
2. Disconnect and reconnect a controller while playing.

Please attach the game's log (launcher → Journal → Export) and, for co-op, the BBSC log (~/.local/share/bbport/user/bbsc/logs/bbsc-mod-*.log) to the issue.

SHA-256: fb5a0ed735b6141c29f412f1a5056e0a687cd059aea153da52737a1bb996d168