Make sure to not change ellipsoid parameters to WGS84 when applying the
null grid. Coordinates will still refer to the input ellipsoid so we
keep the original parameters which in turn will be used when the
coordinates are transformated to/from cartesian/geocentric space.
Adjusted regression test material in nad/proj_outIGNF.dist slightly to
accomodate numerical differences at the mm level. The transformations
in question are at best accurate to about 1m so this shouldn't change
real world usage of these transformations.