Added Plane::operator-() to flip plane, that is surprisingly complex to do properly given existing set of constructors.
Added Plane::operator-() to flip plane, that is surprisingly complex to do properly given existing set of constructors.

paroj/ogre,OGRECave/ogre,OGRECave/ogre,RealityFactory/ogre,paroj/ogre,paroj/ogre,paroj/ogre,RealityFactory/ogre,RealityFactory/ogre,OGRECave/ogre,RealityFactory/ogre,RealityFactory/ogre,OGRECave/ogre,OGRECave/ogre,paroj/ogre