Same interface but less features (push_back, pop_back, clear, size, [] etc).
To prepare for SIMD/SSE code: Added #define ATTRIBUTE_ALIGNED16(a) __declspec(align(16)) a
Added btStackAlloc to Bullet (right now only used by btGjkEpa)
removed default constructors of btCollisionWorld/btDiscreteDynamicsWorld, to reduce link-time dependencies
removed two cached optimizations, type in btTransform and cached inverse transform (todo: test performance impact)
committed fixes that make the code adhere to 'who creates it, also destroys it'