Blender Git Loki

* The displist would be uninitialized when nurbs bezieru/v was set and the order wasnt 3 or 4. add a function that checks nurbs can produce a valid line. check_valid_nurb_u/v
* when check_valid_nurb_u/v fails, no curve is allocated or drawn.
* knotsu/v could be NULL but some functions didn't check for this, make sure this is checked for everywhere.
* The interface didnt change check the order when the bezier u/v flag was set, added functions clamp_nurb_order_u/v that takes into accound the number of points and the bezier u/v flag.