BView: add support for even/odd winding rule

[pulkomandy]

There are two possible way of filling polygons: the "even/odd" and the "non-zero" rules. Haiku currently uses the "non-zero" rule.

Some drawing code in WebKit requires use of the "even/odd" rule. This is the cause of #10214, and probably some other problems.

It would be nice to add a way to change the winding rule, either as an extra argument to FillPolygon and FillShape, or as part of the view state.

Agg supports both winding rules (with agg::fill_even_odd and agg::fill_non_zero constants). Our custom polygon rasterizer seems to have code for handling this, but I don't know if it works.

[pulkomandy]

Implemented in hrev47005.