gio/gobject: Various introspection fixes

gobject/gclosure.c

@@ -755,7 +755,7 @@ g_closure_remove_finalize_notifier (GClosure      *closure,
 /**
  * g_closure_invoke:
  * @closure: a #GClosure
- * @return_value: (allow-none): a #GValue to store the return
+ * @return_value: (optional) (out): a #GValue to store the return
  *                value. May be %NULL if the callback of @closure
  *                doesn't return a value.
  * @n_param_values: the length of the @param_values array

gobject/gsignal.c

@@ -1265,7 +1265,7 @@ g_signal_lookup (const gchar *name,
  * created. Further information about the signals can be acquired through
  * g_signal_query().
  *
- * Returns: (array length=n_ids): Newly allocated array of signal IDs.
+ * Returns: (array length=n_ids) (transfer full): Newly allocated array of signal IDs.
  */
 guint*
 g_signal_list_ids (GType  itype,

gobject/gvaluetypes.c

@@ -1239,7 +1239,7 @@ g_value_set_variant (GValue   *value,
 /**
  * g_value_take_variant:
  * @value: a valid #GValue of type %G_TYPE_VARIANT
- * @variant: (allow-none): a #GVariant, or %NULL
+ * @variant: (nullable) (transfer full): a #GVariant, or %NULL
  *
  * Set the contents of a variant #GValue to @variant, and takes over
  * the ownership of the caller's reference to @variant;