Bullet Physics

This is the bullet physics library.

I'm having trouble with GCC pedantic mode and the test file, so it's not 100% operational, although the actual library appears to build. Any help with this would be appreciated.

I called the package `bullet2` so as to not conflict with a possible future package for the in-development Bullet 3 (https://github.com/erwincoumans/bullet3); people may want to install one or the other depending on what their software is using.

The patch removes some checks for WIN32 which was causing the `bullet.pc` file to not be created, preventing pkg-config from working. I haven't provided this patch to the upstream development because to best of my knowledge Bullet 2 isn't receiving any further work, only Bullet 3.