Addition of 3D physics engine MuJoCo and 2D collision detector libccd

[bottle2]

I'm only aware of their existence and I haven't tested neither.
I'd add them next to Chipmunk2D on the Game Programming category, although they serve other purposes.

MuCoJo - Multi-Joint dynamics with Contact. A general purpose physics simulator. Apache-2.0
libccd - Library for collision detection between two convex shapes. BSD-3-Clause