Layer_Shape: add support for Cairo render using cairo_t*.
In Outline and Layer_Polygon Use Layer_Shape to render though cairo_t*
Layer_Skeleton: add support for Cairo render using cairo_t*.
Remove unneeded headers
FilledRect: add support for Cairo render using cairo_t*.
Halftone2: add support for Cairo render using cairo_t*.
Halftone3: add support for Cairo render using cairo_t*.
LumaKey: add support for Cairo render using cairo_t*.