Curve Angle

some benchmarks, all in microseconds, 100 rings, running average of 100 samples:

574 previous version: no curve angle support
765 curve angle support, but curve angle2 calc commented out
767 curve angle support, but curve angle2 calc skipped by zero test

same test but with 20 sides instead of 5:
1.843 previous version: no curve angle support
2.547 curve angle support, but curve angle2 calc commented out
2.564 curve angle support, but curve angle2 calc skipped by zero test

same test on bad box:
297 previous version: no curve angle support
378 curve angle support, but curve angle2 calc skipped by zero test

Either way best case is curve calc now takes approx. 33% longer. However the good news is the entire point calc is only about 20% of the draw function time *in line mode*.