Physics library updates, continued

When I started using the Chipmunk physics simulation library I did what most programmers do when confronted with unfamiliar code: I rewrote it. It was a good way to learn the ins and outs of the code, and it did integrate better with my own code, but ultimately it meant that I wasn't benefiting from other peoples' continued work on the library. The whole point of libraries is to save work.

I've fixed up the current version of the library to work with my compiler (MS Visual C++) again. Scott Lembcke has accepted the patch into the main repository, so hopefully I can save someone else some work. I've also adapted my lunar lander program to work with the updated stock library, so now I should be able to get upgrades much more easily.

The end result, of course, is that the game looks and behaves exactly the same. I have turrets in an initial state; I will now dive in and work on getting them up to fully operational status.