Use full mesh for collisions on curved walls

[Dewb]

Stacked cube representation of curved walls leads to some funny corner bounces off curved walls. Makes the game a little harder, because you get fewer upwards bounces.

This is probably in nice-to-have territory at this point. I have a partial implementation stashed locally, but it's not working yet.

[t3kt]

We should talk about how that impacts configuration stuff. It shouldn't be too much of a change.

[Dewb]

Yeah, the whole curved wall thing is a bit of a hack right now. I never got around to cleaning up the config stuff because I was stuck on the collisions.

We can use them to create more interesting level designs easily, though. That sweep code can do a lot more than just the rectangular arcs I put in level 1.