Update the bounding boxes of animated skinned meshes.  (Attempt to) remove duplication of the recalculation of frames of animated meshes in CAnimatedMeshSceneNode::OnAnimate() and CAnimatedMeshSceneNode::render().

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@1805 dfc29bdd-3216-0410-991c-e03cc46cb475