swfdisplayitem->skewy() adds ddegrees to current y-skew.
The object may be a swfshape(), a swfbutton(), a swftext() or a swfsprite() object. It must have been added using the swfmovie->add().
See also swfdisplayitem->skewyto(), swfdisplayitem->skewx() and swfdisplayitem->skewxto().