This code uses a custom packet acknowledgement system,
which is more suited for file transfer and does not suffer from
the small sender window used by the default acknowledgement system

This is not ideal either, but I would rather
not use a constant for something unrelated.

Addons menu

See merge request KartKrew/Kart!8

* if you sent it to a client rather than the server, game over, your connection is closed
* if files that don't exist or are too large are requested are listed, game over, your connection is closed (they should have been checked on YOUR side beforehand, silly)
* if the server has downloading disabled anyway, ...yeah, you get the idea

Don't worry, I made sure Got_RequestFilePak cleaned up the full file request list for the node in case of failure

This removes exactly one feature in exchange for a greater number of files to be loaded. I asked around, and people don't actually like what it currently does (load unimportant server-side files if you can findfile it locally), so.

Can be reverted if requested.

-Added a timeout for game state downloading to prevent definitive join freezes in some cases. The timeout has a minimum value of "jointimeout" and gets higher as the game state grows in size
-If the server tries to kick a joiner who is downloading the game state, they will get a timeout instead, because a regular kick would only happen once the game state has been downloaded
-Added a timeout for player ticcmd packets, again to prevent freezes to happen in some cases
-File/game state downloading is now faster, the speed is controlled by the "downloadspeed" cvar, in packets per tic
-The reason is now properly shown when the server refuses connection
-Changed the default values of "nettimeout" to 10 seconds (previously 15) and "maxsend" to 4 MB (previously 1)
-Added a "noticedownload" cvar that displays a message in the server console when someone is downloading a file

(no actual SLOC changes)