format: ordering content of headers

Make gcal-application.h and gcal-event-widget.h the same as
the rest.

src/gcal-application.h

@@ -36,16 +36,16 @@ G_BEGIN_DECLS
 typedef struct _GcalApplicationClass         GcalApplicationClass;
 typedef struct _GcalApplication              GcalApplication;
 
+struct _GcalApplication
+{
+  GtkApplication parent;
+};
+
 struct _GcalApplicationClass
 {
   GtkApplicationClass parent_class;
 };
 
-struct _GcalApplication
-{
-  GtkApplication parent_instance;
-};
-
 GType             gcal_application_get_type     (void) G_GNUC_CONST;
 
 GcalApplication*  gcal_application_new          (void);

src/gcal-event-widget.h

@@ -37,6 +37,11 @@ G_BEGIN_DECLS
 typedef struct _GcalEventWidget                   GcalEventWidget;
 typedef struct _GcalEventWidgetClass              GcalEventWidgetClass;
 
+struct _GcalEventWidget
+{
+  GtkWidget parent;
+};
+
 struct _GcalEventWidgetClass
 {
   GtkWidgetClass parent_class;
@@ -45,11 +50,6 @@ struct _GcalEventWidgetClass
   void (*activate)  (GcalEventWidget *event_widget);
 };
 
-struct _GcalEventWidget
-{
-  GtkWidget parent;
-};
-
 GType         gcal_event_widget_get_type                   (void);
 
 GtkWidget*    gcal_event_widget_new                        (gchar              *uuid);