Splitscreen in netgames

See merge request KartKrew/Kart!22

Specs of dust

See merge request KartKrew/Kart!50

Thundertweak

See merge request KartKrew/Kart!49

You can sometimes have too many rings

See merge request KartKrew/Kart!47

If I were a bad Democam, I wouldn't be sittin' here discussin' it with ya now would I?!

See merge request KartKrew/Kart!48

Prevent spectate griefing

See merge request KartKrew/Kart!43

Singleplayer fixes (no, not record attack, the *other* one)

See merge request KartKrew/Kart!46

Sweet new kicks

See merge request KartKrew/Kart!39

Hard Mode is an unlockable

See merge request KartKrew/Kart!40

Remove most gameplay prints

See merge request KartKrew/Kart!42

* Re-enable the flashing-set thing on attempting to join with the item key. I spoke to Sal privately about this - turns out some keys ALWAYS send key presses instead of only sending one, and shift - what I have item bound to - is one of the problematic ones.
* Make the no-joining-game-after-20-seconds thing happen 20 seconds after the TIMER has started, not the level (ie, take starttime into account)

Play the traditional thundershield manifestation sound when a thundershield is manifested, plus a minor eye towards forward compatibility in the condition for manifestation.

Also, tweak the hoop spawning routine to correctly P_SetTarget the hnexts and hprevs, since I'm mucking around in there.

Some token efforts to make singleplayer mode (accessible only via `-warp` and `map mapxx -force`) not COMPLETELY broken.

* Fixed the conditionals for `suicide` and `retry` commands - `suicide` is now allowed in singleplayer, and `retry` no longer checks your lives (for now).
* Disable the "traditional" level reload method (which `retry` tried to use), since it was completely broken with the other changes we've made. Mapchanges only.
* Made retries cause a mapchange, per the above.
* Disable the last source of skincolor trampling in the game - loading a level while not netgame or record attacking.

(Needs tested)

Fix "advancemap next" going to GHZ at the end of a cup

See merge request KartKrew/Kart!44

`[22:03] TehRealSalt: Not organized code-wise, figured toaster would want to help with that since she's the Menu Queen and she probably has better ideas on how to do it`

The Menu Queen is in the house~ 

* Magical, single-page player select and general netgamey stuff, while still remaining both pretty and functional.
* Death to NOFOURPLAYER, now that the cat's out the bag.
* Clean up NONET, assuming people try to make DD builds on release.
* Minor tweaks across the board, mostly places where I wanted to pilfer minor code from and realised it wasn't done optimally originally.

Next-merge plus rain

See merge request KartKrew/Kart!41

Engine tune-up

See merge request KartKrew/Kart!45

Now that we figured out that the sound cut-outs were due to a race condition and not this option, I feel content putting it with these other engine tweaks.

Minor priority change to two voice lines; the "passing someone" line has the same priority as every other line, and gave it's boosted priority to the way more gameplay-important "hit 'em" line.

Sryder's request

NOW this is good enough to ship

Plus, this is generally better, as a mod could let you unlock stuff "out-of-order"