Blender Git Loki

Freestyle: Partial fix for thinning strokes due to flipping stroke directions at TVertices.

A description of the problem is found in https://developer.blender.org/T36425#19 .

The cause of the issue was identified as roudning errors in Operators::createStroke() due
to insufficient numerical precision. Precision promotion from float to double was done in
the return values of getPoint3D/2D methods in Interface0D and its subclasses in C++
(data members stored in the 0D classes have already been in double precision).