add chipmunk physics package

How do I know the test ran successfully?

```
$ make chipmunk
[target]   i686-pc-mingw32.static with 1 goal from command line
[build]    chipmunk
[done]     chipmunk
```
This should mean that without the changes the recipe is wrong as well. And if the unmodified recipe works, then my change is probably wrong.

Another note: you should comment out these two lines as they hardcode install paths, while cmake does the correct way automatically:

https://github.com/slembcke/Chipmunk2D/blob/master/src/CMakeLists.txt#L25 and https://github.com/slembcke/Chipmunk2D/blob/master/src/CMakeLists.txt#L40

The first one makes the package violate commit checklist # 3 and 4 (in shared mode).
The second one shouldn't matter, but just comment it out for consistency.