Fix T71137: minimum twist mode produces discontinuity in last point for cyclic curves.
This bug was closed for inactivity, but the issue remains present in master.
The minimum twist computation for a curve produced a discontinuity in last vertex of closed (cyclic) curves.
This was invisible for planar curves (2D or 3D), but was made evident when some 'extrusion' or 'bevel' was applied and
when there was some twist or tilt, in particular with low curve 'resolution' settings, or when a symmetric result would
be expected.
The fix: the minimum twist computation was starting at the last vertex instead of the first one.
Tested with non-cyclic curves, doesn't seem to affect previous behaviour.
The curve below is symmetrical about the x-axis, but previously would produce asymmetric bevel or extrude:
Before:
{F10221021}
After:
{F10221025}