Bugfix for degenerate polygons with only two control points.
Bugfix for degenerate polygons with only two control points.

svn path=/trunk/libavg/; revision=3489

scotty007/libavg,th3infinity/libavg,libavg/libavg,yyd01245/libavg,scotty007/libavg,scotty007/libavg,libavg/libavg,hoodie/libavg,th3infinity/libavg,hoodie/libavg,libavg/libavg,th3infinity/libavg,hoodie/libavg,hoodie/libavg,th3infinity/libavg,yyd01245/libavg,yyd01245/libavg,yyd01245/libavg,scotty007/libavg,libavg/libavg