QSizePolicy: add Q_FLAGS(ControlTypes)

There's no reason not to have it, and it allows better debug output.

[ChangeLog][QtWidgets][QSizePolicy] QSizePolicy::ControlTypes is now
introspectable through QSizePolicy's meta object.

Change-Id: Ia274c708f31e735e4605bd4769aa65a9b78d690f
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/widgets/kernel/qsizepolicy.h

@@ -45,6 +45,7 @@ class Q_WIDGETS_EXPORT QSizePolicy
 {
     Q_GADGET
     Q_ENUMS(Policy)
+    Q_FLAGS(ControlTypes)
 
 public:
     enum PolicyFlag {