Blender Git Loki

Another possible fix for degenerate triangles in imported mesh data.

A motivating example of the problem the present solution aims to address is a
quad face such that three of the four vertices are colinear (i.e., they are
lying on a line). Depending on how this quad is separated into two triangles,
one of them can be a degenerate triangle. Degenerate triangles of this form
are easy to avoid by rotating the diagonal edge of quad faces without affecting
the visual outcome. The fix implemented in this commit tries to address
degenerate triangles in this way.