Negative extrude height leads to malformed output

[WJWH]

The following extopenscad code:

linear_extrude(-5) square(5);

will lead to a cube where normal vectors of the top and bottom faces are pointing inwards instead of outwards. I believe this is caused by the extrusion algorithm falsely assuming that all extrusions will have positive heights and setting the normal vectors based on that.

[julialongtin]

hmm. now this doesn't work at all. :D