Bug fix in mesh extrusion for non-constant layer depth reported by cwilson.
Bug fix in mesh extrusion for non-constant layer depth reported by cwilson.

iakovos-panourgias/fluidity,iakovos-panourgias/fluidity,rjferrier/fluidity,rjferrier/fluidity,jrper/fluidity,jjo31/ATHAM-Fluidity,iakovos-panourgias/fluidity,iakovos-panourgias/fluidity,jrper/fluidity,jjo31/ATHAM-Fluidity,jrper/fluidity,jjo31/ATHAM-Fluidity,rjferrier/fluidity,jrper/fluidity,iakovos-panourgias/fluidity,jrper/fluidity,rjferrier/fluidity,rjferrier/fluidity,jjo31/ATHAM-Fluidity,jjo31/ATHAM-Fluidity