Introduce kF_UseGjkConvexCastRaytest, and make kF_UseSubSimplexConvexCastRaytest the default for btCollisionWorld::rayTest See https://github.com/bulletphysics/bullet3/issues/34

Add btCollisionObject::setIgnoreCollisionCheck to disable collisions between specific instances, without having a btTypedConstraint. See https://github.com/bulletphysics/bullet3/issues/165

Make btMultiBody and btMultiBodyJointMotor backwards compatible with Bullet 2.82 API (single-DOF API)