Merge from vendor branch TNF:

Merge from vendor branch TNF:
Initial import of bullet-2.76:

Bullet is a 3D Collision Detection and Rigid Body Dynamics Library
for games and animation.  Free for commercial use, including
Playstation 3, open source under the ZLib License.  Discrete and
continuous collision detection, integrated into Blender 3D, and
COLLADA 1.4 Physics import.