Rewrite of the ed_editcurve_extrude function to behave differently under certain conditions.
I forgot to change the weight and radius. I also added some new comments and added a new test to prevent an assert in BKE_nurb_bpoint_get_next/BKE_nurb_bezt_get_next from failing.
I am not sure how this fit with D2445
Isn't this fixed now? Is there still something that needs changing?