Before they were 1/2 treated as flags and 1/2 treated as a mode enum.
The ERC flag relaxes constraints on data that is settable in the
schematic editor.
Fixes https://gitlab.com/kicad/code/kicad/issues/11018
Also fixes some plot bugs with arcs.
Also moves polygonization of arcs (when required) in plotting code
from 5 degrees to calculated based on ARC_HIGH_DEF.
Fixes https://gitlab.com/kicad/code/kicad/issues/5017