Blender Git Loki

Fix T40758 Front facing not consistent in sculpt mode.

Some tools used view vector while others used the area normal.

Area Normal -is- useful and it will have to be incorporated to the
system better, but I'd like to do it in a way that is well
collaborating with sculpt plane calculation too, because it will have
to be slightly more expensive, i.e normal calculated before the plane,
never together, so only front to the area normal influence can be kept.

Currently sculpt plane takes into consideration view vector, but that
can produce an unwanted normal/plane at glancing angles on mesh edges.

Another issue that arises here is whether we do an actual calculation of
sculpt normal for each symmetry pass or we just flip the initial (former
is more expensive but more correct)