Customizable Menu Controls V2

Customizable Menu Controls, round 2 (and also version 2).

Pros:

• Most importantly, customizable menu controls!
• The intro, credits, and continue screens (and I believe also custom between-level cutscenes) now also accept certain user-set controls.
• The "menu ding" now plays in many more circumstances, like opening the pause menu, or closing it, or pressing the cancel/back button.

Cons:

• The "menu ding" might play in too many circumstances. Please test it out and provide some feedback and such.
• Some of my coding is probably horrendous, either readability-wise or performance-wise, maybe even both.
• Still most likely has to be ported manually to version 2.2.
• ...It looks like I made the commits with "customizable controls" instead of "customizable menu controls" in the description thing.

Compared to the previous merge request:

• Some things are a bit better written, both readability- and performance-wise... I think.
• I did not make the "consoleready" variable globally available this time.
• Default menu controls have been added, both for the standard computer version and the various console ports, although I'm unable to test the ports. (However, the default menu controls won't be initialized if config.cfg exists or something, which it most likely will for people playing SRB2 before version 2.1.17 (if that's going to be a thing).) For computers, mouse left-click is set to "confirm" and mouse right-click to "cancel/go back". (As controllers will need to be set up in general for SRB2 anyway, I didn't include controller controls for the computer version.)
• Edit: Also, the menu control order has been changed from "up, down, next, previous" to "up, down, previous, next", to make it more "up, down, left, right"-ish like the other left/right controls.
• Same edit: The console command has also been changed from "setmenucontrol" to "setcontrolmenu", to be more in line with "setcontrol"/"setcontrol2" having the "2" for player 2 at the end.

Like last time, though, this will still benefit from this wad archive containing a thin-font comma, still having a .zzz extension rather than .wad. Also like last time, please test this extensively before merging it.