Turn ClutterBindingPool a GObject

ClutterBindingPool is already "problematic" in terms of memory
management for language bindings and gobject-introspection. It
also lacks a GType.

Turning ClutterBindingPool into a GBoxed would not make much
sense, since it does not adhere to the copy/free semantics. It
could be referenced/unreferenced, but in that case we can just
as well use GObject as a base class instead of reimplemeting
a ref-counted object and then boxing it.

ClutterBindingPool is obviously a terminal class, so we just
hide the instance and class structures.

clutter/clutter-binding-pool.h

@@ -33,6 +33,18 @@
 
 G_BEGIN_DECLS
 
+#define CLUTTER_TYPE_BINDING_POOL       (clutter_binding_pool_get_type ())
+#define CLUTTER_BINDING_POOL(obj)       (G_TYPE_CHECK_INSTANCE_CAST ((obj), CLUTTER_TYPE_BINDING_POOL, ClutterBindingPool))
+#define CLUTTER_IS_BINDING_POOL(obj)    (G_TYPE_CHECK_INSTANCE_TYPE ((obj), CLUTTER_TYPE_BINDING_POOL))
+
+/**
+ * ClutterBindingPool:
+ *
+ * Container of key bindings. The #ClutterBindingPool struct is
+ * private.
+ *
+ * Since: 1.0
+ */
 typedef struct _ClutterBindingPool      ClutterBindingPool;
 
 /**