For the c++ api dox this expands to "\c nullptr" (the
\c directive indicates a code literal value), and for sipify/Python
it expands to ``None`` (`` is sphinx annotation for literal values)
Makes for nicer dox for both c++ and Python!
This new option, available under the "Advanced" button for fill symbols,
allows forcing rendered polygons to follow the standard "right hand
rule" for ring orientation (where exterior ring is clockwise, and
interior rings are all counter-clockwise).
The orientation fix is applied while rendering only, and the original
feature geometry is unchanged.
This allows for creation of fill symbols with consistent appearance,
regardless of the dataset being rendered and the ring orientation
of individual features.
Refs #12652
