User-mappable buttons in WASD and SDL2 mods

[Clownacy]

This should be easy, really. From the user's point of view, there should just be a 'settings.txt' that looks like this:

jump = z
shoot = x
up = up
down = down
left = left
right = right

...Actually, now that I think about it, virtual vs. physical key locations will be tricky. I can just see the flood of '';' doesn't actually use ';'' issues already.

Well, this won't be an issue for controllers anyway... or will it? I guess I can just force XInput button names.

Or maybe even SDL2's own keycodes. They're not something I can just expect the user the know, however, so I may need to add comment support first.