Renamed BevPoint's members
* x,y,z -> vec[3]; compatible with other functions.
* f1 -> split_tag; used by displist to set the splitting flag.
* f2 -> dupe_tag; used in curve.c to remove duplicates.
BevList
* flag -> dupe_nr; was being used as a counter for duplicate points.
* use arithb.c functions where possible.
* arrays for coords, tilt and radius were being allocated, then copied into the BevPoint's, now write directly into the values without allocing/freeing arrays.
2fc4ee3545