WT-11772: Resolve some Wredundant-move warnings

These warnings are the result of unnecessary `std::move` calls. The
unique pointer is constructed in a class method, but as an lvalue. So
the ownership never is assigned to the class, due to copy elision.

Author: matthias

src/Wt/Auth/AuthWidget.C

@@ -211,7 +211,7 @@ std::unique_ptr<WWidget> AuthWidget::createRegistrationView(const Identity& id)
 
   std::unique_ptr<RegistrationWidget> w(new RegistrationWidget(this));
   w->setModel(std::move(model));
-  return std::move(w);
+  return w;
 }
 
 void AuthWidget::letResendEmailVerification()
@@ -371,7 +371,7 @@ std::unique_ptr<WWidget> AuthWidget::createFormWidget(WFormModel::Field field)
     result.reset(new WCheckBox());
   }
 
-  return std::move(result);
+  return result;
 }
 
 void AuthWidget::updatePasswordLoginView()

src/Wt/Auth/RegistrationWidget.C

@@ -92,7 +92,7 @@ std::unique_ptr<WWidget> RegistrationWidget
     result.reset(p);
   }
 
-  return std::move(result);
+  return result;
 }
 
 void RegistrationWidget::update()

src/Wt/Auth/UpdatePasswordWidget.C

@@ -111,7 +111,7 @@ std::unique_ptr<WWidget> UpdatePasswordWidget
     result.reset(p);
   }
 
-  return std::move(result);
+  return result;
 }
 
 void UpdatePasswordWidget::checkPassword()

src/Wt/Chart/WCartesianChart.C

@@ -1976,7 +1976,7 @@ std::unique_ptr<WWidget> WCartesianChart::createLegendItemWidget(int index)
   label->setVerticalAlignment(AlignmentFlag::Top);
   legendItem->addWidget(std::move(label));
 
-  return std::move(legendItem);
+  return legendItem;
 }
 
 void WCartesianChart::addDataPointArea(WT_MAYBE_UNUSED const WDataSeries& series,

src/Wt/Chart/WPieChart.C

@@ -175,7 +175,7 @@ WPieChart::createLegendItemWidget(int index, WFlags<LabelOption> options)
     }
   }
 
-  return std::move(legendItem);
+  return legendItem;
 }
 
 void WPieChart::paint(WPainter& painter, const WRectF& rectangle) const

src/Wt/WAbstractItemView.C

@@ -1245,7 +1245,7 @@ std::unique_ptr<WWidget> WAbstractItemView::createHeaderWidget(int column)
   if (!sc.empty())
     result->addStyleClass(sc);
 
-  return std::move(result);
+  return result;
 }
 
 void WAbstractItemView::enableAjax()

src/Wt/WBoxLayout.C

@@ -277,7 +277,7 @@ std::unique_ptr<WWidget> WBoxLayout::createSpacer(const WLength& size)
       spacer->setMinimumSize(WLength::Auto, size);
   }
 
-  return std::move(spacer);
+  return spacer;
 }
 
 void WBoxLayout::setResizable(int index, bool enabled,

src/Wt/WClientGLWidget.C

@@ -1206,7 +1206,7 @@ std::unique_ptr<WResource> WClientGLWidget::rpdToMemResource(WRasterImage *rpd)
   std::unique_ptr<WMemoryResource> mr(new WMemoryResource("image/png"));
   mr->setData(reinterpret_cast<const unsigned char*>(ss.str().c_str()),
               ss.str().size());
-  return std::move(mr);
+  return mr;
 }
 #endif
 

src/Wt/WDoubleSpinBox.C

@@ -127,11 +127,7 @@ std::unique_ptr<WValidator> WDoubleSpinBox::createValidator()
   std::unique_ptr<WDoubleValidator> validator(new WDoubleValidator());
   validator->setMandatory(true);
   validator->setRange(min_, max_);
-#ifndef WT_TARGET_JAVA
-  return std::move(validator); // FreeBSD wanted this std::move
-#else // WT_TARGET_JAVA
   return validator;
-#endif // WT_TARGET_JAVA
 }
 
 WT_USTRING WDoubleSpinBox::textFromValue() const

src/Wt/WItemDelegate.C

@@ -437,7 +437,7 @@ std::unique_ptr<WWidget> WItemDelegate
                      WLength(100, LengthUnit::Percentage)); //for Konqueror
   result->addWidget(std::move(lineEdit));
 
-  return std::move(result);
+  return result;
 }
 
 void WItemDelegate::doCloseEditor(WWidget *editor, bool save) const