[Nel] Fixes to snowballs2 for VS 7.1

[Codemaster]

animation.cpp:
change  AnimationSet = Scene->createAnimationSet ();
to      AnimationSet = Driver->createAnimationSet ();
add     #include <nel/3d/u_driver.h>

mouse_listener.h
add
        NLMISC::IEventListener &getEventListenerInterface() { return *this; }


The rest of the small errors that come up are easily fixed... i may place 
another email showing how to fix those, too.