IK solver may move pelvis

[kkevlar]

The end of the PDIK phase of the IK solver depends on the distance from the body to the target, but does not take into account any amount that the pelvis could have diverged from its starting position. The pelvis is held in place with m->qpos_spring during the PDIK process, but this spring is not infinitely rigid and the pelvis could be diverging bit by bit with every IK-based transformation.