Surface: Fix several clazy issues:

* Missing reference in range-for with non trivial type [-Wclazy-range-loop-reference]
* Use multi-arg instead [-Wclazy-qstring-arg]

src/Mod/Surface/App/FeatureSewing.cpp

@@ -86,7 +86,7 @@ App::DocumentObjectExecReturn *Sewing::execute(void)
                 Part::TopoShape ts = static_cast<Part::Feature*>(it->first)->Shape.getShape();
 
                 //we want only the subshape which is linked
-                for (auto jt: it->second) {
+                for (const auto& jt: it->second) {
                     TopoDS_Shape sub = ts.getSubShape(jt.c_str());
                     builder.Add(sub);
                 }