Bug#860789: freecad: import of openscad file turns "differences" into "unions"

[Petter Reinholdtsen]

Control: forwarded -1 https://github.com/FreeCAD/FreeCAD/issues/9877

I created a github issue for the problem, and tracked down that the fix
for it is already upstream, and should show up in version 0.21 of
FreeCAD.

The github issue got links to the fixes and test case, if someone want
to backport a fix for this.  I do not see the point myself, as it is
trivial to remove the problematic 'union();' parts from a OpenSCAD file.

-- 
Happy hacking
Petter Reinholdtsen