Blender Git Loki

Fix T37510 Knife missed cuts on small faces.

For very thin faces, knife sometimes missed cutting a few.
Problem was that a test for edges being totally inside a face
was being applied in inappropriate circumstances. An assumed
invariant about the knife hit structure is not true when
actually in the middle of making cuts.
Also make a 'big epsilon' a little smaller, though don't think
that was the problem in this bug.