This is the first step to allowing non-segments in the line chain.
External routines cannot be allowed to change the line chain without
going through the internal routines. To accomplish this, we remove the
Vertex() and Point() access routines and only leave the const versions.
Transformations are given for both points as well as the chain itself.
* rename WS_DRAW_ITEM_POLYGON to WS_DRAW_ITEM_POLYPOLYGONS (better name)
* use SHAPE_POLY_SET instead of std::vector(<wxPoint> to manage the set of polygons.
It also remove duplicate code related to HitTest and bounding box.
* fix HitTest and WS_DRAW_ITEM_POLYGON highlight.
Mark Roszko
Seth Hillbrand
jean-pierre charras
Jeff Young
Jon Evans