Fix [#26474] double_sided wrong in COLLADA Export

reported by Juan Linietsky

The export was not really wrong, but Maya expects their profile to be present inside <geometry>. Added this for mesh with ME_TWOSIDED flag set.

Ideally this will change in the future to be controllable through options to the exporter (like current Google Earth and 3DS Max extensions for <double_sided>).

source/blender/collada/GeometryExporter.cpp

@@ -116,6 +116,11 @@ void GeometryExporter::operator()(Object *ob)
 	}
 	
 	closeMesh();
+	
+	if (me->flag & ME_TWOSIDED) {
+		mSW->appendTextBlock("<extra><technique profile=\"MAYA\"><double_sided>1</double_sided></technique></extra>");
+	}
+	
 	closeGeometry();
 	
 #if 0