Blender Git Loki

Fix for stroke rendering instability with stroke geometry shaders.

* Stroke::Resample(int nPoints) was not properly working when a wrong
value was returned from Stroke::getLength2D(), resulting in repeated
warning messages "Warning: incorrect points number" during stroke
rendering. The main cause was that stroke geometry shaders did not
update the two-dimensional (2D) length (also referred to as curvilinear
abscissa) after they modified the 2D points of stroke vertices. Now
all stroke geometry shaders make explicit calls for Stroke::UpdateLength()
that has been introduced for recomputing the 2D length. Many thanks to
Josef who reported the problem together with sample .blend files for
reproducing the issue.

* Missing Python wrapper of Stroke::getLength2D() was added.