cxx: Add srb2::Overload for using std::visit

See merge request KartKrew/Kart!879

cxx: Convert sdl/i_video.cpp

See merge request KartKrew/Kart!872

Lightsnake polish

Closes #309 and #299

See merge request KartKrew/Kart!870

Apply tiregrease exception to offroad TERRAIN

See merge request KartKrew/Kart!866

Stricter compbranch and comprevision

Closes #398

See merge request KartKrew/Kart!864

Decrease spinouttimer every other tic in lightsnake, to a minimum of 1 to still prevent drop dashing

Resolves #309.

Permit a lightsnaking player to go into RESPAWNST_DROP (the final second of lightsnake) early at any time after the initail bring-back-to-last-waypoint.

Needs balance testing, but resolves #299.

Clean up memory mishandling flagged by DrMemory

See merge request KartKrew/Kart!863

SDL: only react to window focus changes if state actually changes

See merge request KartKrew/Kart!859

Fixes -Wunused-function

Print musicdef along with tunes -show

See merge request KartKrew/Kart!854

Fix audio/music_player.cpp compiler error on 64-bit

See merge request KartKrew/Kart!858

Monitors

See merge request KartKrew/Kart!845

Make save_p / savebuffers not global

See merge request KartKrew/Kart!834

Moves `P_Net(Un)ArchiveTubeWaypoints` down the file to take advantage of `SaveMobjnum` inline.

g_demo.c is officially No Man's Land

- `skyboxcenterpnts` and `skyboxviewpnts`
    - P_InitSkyboxPoint`, which calls `P_SetTarget`
- `waypoint->mobj`
    - Make sure NULL before using `P_SetTarget` on
- `tubewaypoints`
    - Use `P_SetTarget`
    - Use `UINT32_MAX` for the invalid mobjnum, since 0 is a valid one.
- `waypointcap` and `kitemcap`
    - NULL before reset

Our international nightmare is over.

core: load exchndl.dll at runtime, RINGRACERSWADDIR

See merge request KartKrew/Kart!857

Reduce stair janking loss of control if momentum angle drifts too far from facing angle

See merge request KartKrew/Kart!850

Add S_FindMusicDef, function to find musicdef by name

See merge request KartKrew/Kart!860

Go to addons folder by default in addons menu

Closes #373

See merge request KartKrew/Kart!853