app_server & interface kit: support fill rules.

* BView gets SetFillRule/FillRule methods. The fill rule is part of the
view state.
* The B_NONZERO rule is the default. This is what we implemented before.
* The B_EVEN_ODD rule is the other common possibility for this, and
we need to support it to help WebKit to render properly.

headers/os/interface/InterfaceDefs.h

@@ -261,6 +261,14 @@ enum cap_mode {
 const float B_DEFAULT_MITER_LIMIT = 10.0F;
 
 
+// Polygon filling rules
+
+enum {
+	B_EVEN_ODD = 0,
+	B_NONZERO
+};
+
+
 // Bitmap and overlay constants
 
 enum bitmap_tiling {