Add warning and reset flow for non-default masterserver address

See merge request KartKrew/Kart-Public!277

backport P_CheckSight from vanilla

See merge request KartKrew/Kart-Public!273

2.2 Backports - add ceil slope double step-up/down and fix sprite/models all black in sector with light level of 256

See merge request KartKrew/Kart-Public!274

Uncapped

See merge request KartKrew/Kart-Public!276

Makes the displayed FPS more accurate to what it's actually displaying.

Also removed HUDTRANS from it -- stop it fading out during level transitions, it's annoying when I actually want to see the FPS during those bits.

Fixes KartKrew/Kart-Public#10

Was done this way for the sake of an older version of uncapped's timing; now that the new timing is much better, I decided it should remain as close to pre-uncapped as it can be.

Advertise_OnChange is CV_NETVAR, so the server will get registered by CV_LoadNetVars when the server starts.

This race condition occasionally pops up in master, but got very consistent with uncapped.

Not the cause of the black sky bug, but doing this helped me diagnose it & it's cleaner

Fixes Software being a blank screen

Fixes weirdness with the named values in fpscap

Makes me unable to compile with harsh compiler settings