Another fix to CSceneCollisionManager::getPickedNodeBB(). Ensure that the collision point with the plane of a box is actually on the box surface rather than outside it.  Retested with regression test and example 07.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@2048 dfc29bdd-3216-0410-991c-e03cc46cb475