improve trimmed curve handling in both kernels

src/ifcgeom/taxonomy.h

@@ -251,9 +251,11 @@ struct trimmed_curve : public curve {
 
 	// @todo somehow account for the fact that curve in IFC can be trimmed curve, polyline and composite curve as well.
 	item* basis;
-	bool orientation;
 
-	trimmed_curve() : basis(nullptr), orientation(true) {}
+	// @todo does this make sense? this is to accomodate for the fact that orientation is defined on both TrimmedCurve as well CompCurveSegment
+	boost::optional<bool> orientation_2;
+
+	trimmed_curve() : basis(nullptr), orientation_2(true) {}
 	
 	virtual void reverse() {
 		// std::swap(start, end);