This is needed because displacement might been interpolated from a grid
with different orientation and in this case X and Y components of displacement
are need to be flipped in needed order.
Order of flipping is determining by projecting source grids axis orientation
on target grid axis. This probably will give some unwanted artifacts when
interpolating non-planar face but currently can't think about better way
to determine how to flip displacement.
This commit makes operators like Subdivide works much more unpredictable
for sculpting data, but this stuff should be rethinked much more global
because current approach is not acceptable.
b2fd08c754