modify own changes to is_quad_convex_v3() to allow quads with a co-linear side to be considered convex (as it did in last release).
this is needed so zero area faces be dealt with by beauty fill.


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@54548 954f8c5b-7b00-dc11-b283-0030488c597c