introspection: Skip some C-only structures

The ParamSpec sub-classes we define are meant to be used only from the C
API, as high-level languages completely ignore them.

The ClutterStageWindow interface is an internal type that escaped into
the public headers; all its methods are private, but we cannot remove
the type until we break for 2.0.

clutter/clutter-color.h

@@ -121,14 +121,14 @@ void          clutter_color_interpolate (const ClutterColor *initial,
 typedef struct _ClutterParamSpecColor  ClutterParamSpecColor;
 
 /**
-  * ClutterParamSpecColor:
-  * @default_value: default color value
-  *
-  * A #GParamSpec subclass for defining properties holding
-  * a #ClutterColor.
-  *
-  * Since: 1.0
-  */
+ * ClutterParamSpecColor: (skip)
+ * @default_value: default color value
+ *
+ * A #GParamSpec subclass for defining properties holding
+ * a #ClutterColor.
+ *
+ * Since: 1.0
+ */
 struct _ClutterParamSpecColor
 {
   /*< private >*/

clutter/clutter-fixed.h

@@ -51,7 +51,7 @@ G_BEGIN_DECLS
 typedef struct _ClutterParamSpecFixed   ClutterParamSpecFixed;
 
 /**
- * ClutterParamSpecFixed
+ * ClutterParamSpecFixed: (skip)
  * @minimum: lower boundary
  * @maximum: higher boundary
  * @default_value: default value

clutter/clutter-stage-window.h

@@ -11,7 +11,7 @@ G_BEGIN_DECLS
 #define CLUTTER_STAGE_WINDOW_GET_IFACE(obj)     (G_TYPE_INSTANCE_GET_INTERFACE ((obj), CLUTTER_TYPE_STAGE_WINDOW, ClutterStageWindowIface))
 
 /**
- * ClutterStageWindow:
+ * ClutterStageWindow: (skip)
  *
  * <structname>ClutterStageWindow</structname> is an opaque structure
  * whose members should not be accessed directly
@@ -22,7 +22,7 @@ typedef struct _ClutterStageWindow      ClutterStageWindow; /* dummy */
 typedef struct _ClutterStageWindowIface ClutterStageWindowIface;
 
 /**
- * ClutterStageWindowIface:
+ * ClutterStageWindowIface: (skip)
  *
  * The interface implemented by backends for stage windows
  *

clutter/clutter-units.h

@@ -145,7 +145,7 @@ gchar *         clutter_units_to_string        (const ClutterUnits *units);
 typedef struct _ClutterParamSpecUnits   ClutterParamSpecUnits;
 
 /**
- * ClutterParamSpecUnits:
+ * ClutterParamSpecUnits: (skip)
  * @default_type: default type
  * @default_value: default value
  * @minimum: lower boundary