Not, I tried using `dist_signed_squared_to_plane_v3` but profiling showed that
it is 50% slower than using regular `mul_v3_m4v3` for the verts.
I managed to get this number closer when manually inlining all the functions
called by `dist_signed_squared_to_plane_v3`. But still `mul_v3_m4v3` was better
and it makes the code simpler to understand.
Also I'm changing the default mode to positive, no idea why it was negative as
default in the first place.
Last but not least, the operator only works well on redo. This was a problem
before, not introduced by this patch.
ce34f9348f