- Clean up PolyTriangleDrawer API so that it can better support both softpoly and the swrenderer

- Slightly improve how softpoly processes portals
- Pass the vertex transform matrix via a command rather than being part of the drawer args
- Improve zbuffer drawers in the software renderer
- Misc model rendering fixes

src/swrenderer/r_swcanvas.cpp

@@ -401,7 +401,7 @@ void SWCanvas::DrawLine(DCanvas *canvas, int x0, int y0, int x1, int y1, int pal
 		palColor = PalFromRGB(realcolor);
 	}
 
-	canvas->Lock();
+	canvas->Lock(true);
 	int deltaX, deltaY, xDir;
 
 	if (y0 > y1)