Revert "Merge branch 'linewidth-backport-qt-before-5.7' into 'master'"

This reverts merge request !12 (merged)

OpenMesh/OMPropertyVisualizerVector2T.cc

@@ -71,8 +71,7 @@ OMPropertyVisualizerVector2<MeshT, VectorType>::OMPropertyVisualizerVector2(Mesh
     {
         w->vectors_edges_rb->hide();
     }
-    // starting with Qt 5.7, use QOverload<double>::of(&QDoubleSpinBox::valueChanged)
-    this->connect(w->lineWidth, static_cast<void (QDoubleSpinBox::*)(double)>(&QDoubleSpinBox::valueChanged),
+    this->connect(w->lineWidth, QOverload<double>::of(&QDoubleSpinBox::valueChanged),
                   [this](double value) {lineNode->set_line_width(value);});
 }