* plugins/directx/vout_directx.*: the directx vout plugin now uses the
IID_IDirectDrawSurface2 interface, this shouldn't break anything and we should now
support WinNT4+DirectX3.
Added support for YUY2 overlays because a few graphics cards only support this.
Some code cleanup too.
* plugins/directx/vout_events.c: small bugfix.