UI: Fix warnings for Qt 5.15

AllDockWidgetFeatures is now deprecated. Use underlying values instead.

Use default QFlags constructor instead of nullptr/0.

Use QWheelEvent::angleDelta() in place of orientation() and delta(), and
position() in place of x() and y().

UI/window-basic-main.cpp

@@ -221,7 +221,9 @@ OBSBasic::OBSBasic(QWidget *parent)
 
 	statsDock = new OBSDock();
 	statsDock->setObjectName(QStringLiteral("statsDock"));
-	statsDock->setFeatures(QDockWidget::AllDockWidgetFeatures);
+	statsDock->setFeatures(QDockWidget::DockWidgetClosable |
+			       QDockWidget::DockWidgetMovable |
+			       QDockWidget::DockWidgetFloatable);
 	statsDock->setWindowTitle(QTStr("Basic.Stats"));
 	addDockWidget(Qt::BottomDockWidgetArea, statsDock);
 	statsDock->setVisible(false);
@@ -6982,7 +6984,9 @@ void OBSBasic::on_lockUI_toggled(bool lock)
 {
 	QDockWidget::DockWidgetFeatures features =
 		lock ? QDockWidget::NoDockWidgetFeatures
-		     : QDockWidget::AllDockWidgetFeatures;
+		     : (QDockWidget::DockWidgetClosable |
+			QDockWidget::DockWidgetMovable |
+			QDockWidget::DockWidgetFloatable);
 
 	QDockWidget::DockWidgetFeatures mainFeatures = features;
 	mainFeatures &= ~QDockWidget::QDockWidget::DockWidgetClosable;
@@ -7652,7 +7656,9 @@ QAction *OBSBasic::AddDockWidget(QDockWidget *dock)
 	bool lock = ui->lockUI->isChecked();
 	QDockWidget::DockWidgetFeatures features =
 		lock ? QDockWidget::NoDockWidgetFeatures
-		     : QDockWidget::AllDockWidgetFeatures;
+		     : (QDockWidget::DockWidgetClosable |
+			QDockWidget::DockWidgetMovable |
+			QDockWidget::DockWidgetFloatable);
 
 	dock->setFeatures(features);