Customizable Menu Controls

This is it, customizable menu controls are ready and stuff after 18 days in development. Started on the 21st September 2016, finished on the 8th October 2016 (and the last week was while sick, could have been 2-3 days faster or so).

Pros:

• ...Well, customizable menu controls!
• There are now sounds for opening the menu and going back in the menu and such, as well as other times where they were obviously just missing.
• Made "ESC" vs "Escape" stuff more consistent (now always says "Escape", not "ESC").
• The "release Shift while holding other Shift un-Shifts" issue is fixed too.
• The width check for control name lengths and that also applies to non-menu controls (can be observed by using the left/right arrow keys on the same control).
• The intro, credits, and continue screens are now skip-able and such through the user-set controls (as well as Enter and Escape, hardcodedly). Specifically the "confirm", "cancel" and "open menu" menu controls, and the "jump" movement control. (Escape and the "cancel" menu controls don't apply for the continue screen.)
• I get to be in the credits, under the name "Zwip-Zwap Zapony" (with quotes). On second thought, this is probably not up to me to decide.
• Lots of code for you all to try wrapping your head around to optimize, in the good way by giving you a nice brain challenge.

Cons:

• Lots of code for you all to try wrapping your head around to optimize, in the bad way by (probably) not being very optimized. I don't know much about coding in C or related languages.
• There are no "default" menu control remappings for controllers or mice anymore, so the keyboard has to be used at least a bit to set up menu controls for controllers/mice.
• Almost definitely has to be ported manually for 2.2, and there's a lot of stuff that will probably confuse others than me, leading it to being implemented either too little, too much, or post-2.2.0 (considering I won't have access to the 2.2 code to port it myself until 2.2 is released).

Edit: Oh, also, please test this extensively before merging it. I can only test it so much on my own, and I only have one compiler.

Edit 2: And don't forget the contents of this Wad file (with a ZZZ extension)!