Blender Git Loki

Fix #21827: Outer portions of extruded 2D curves do not render correctly

DispList->rt is used by render stuff to set vlak flags. This rt field is setting
to nurbs's flags in displist creation function. Possible flags for nurbs are
CU_SMOOTH and CU_2D. CU_SMOOTH is ok, but CU_2D conflicts with R_NOPUNOFLIP.

I cleared rt's CU_2D flag. Don't forget about possible conflicts if new
nurbs flags will be added.