QFontDialog: optimize allocation of QFontDialogOptions

Use QSharedPointer::create(), to fuse control block and
payload into a single memory allocation.

Change-Id: I8d87c73566c3be960e957ec0b5419a77da2fc8c9
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

src/widgets/dialogs/qfontdialog.cpp

@@ -103,7 +103,8 @@ static const Qt::WindowFlags DefaultWindowFlags =
         Qt::Dialog | Qt::WindowSystemMenuHint;
 
 QFontDialogPrivate::QFontDialogPrivate()
-    : writingSystem(QFontDatabase::Any), options(new QFontDialogOptions)
+    : writingSystem(QFontDatabase::Any),
+      options(QSharedPointer<QFontDialogOptions>::create())
 {
 }