[glib] gobject: fix G_DEFINE_TYPE_EXTENDED docs so code snippet actually compiles

[Andrés Aragoneses <aaragoneses src gnome org>]

commit 859e4239c575a0e597f32d017d6012be7b4d3ab8
Author: Andres G. Aragoneses <knocte gmail com>
Date:   Thu Apr 4 12:10:28 2013 +0100

    gobject: fix G_DEFINE_TYPE_EXTENDED docs so code snippet actually compiles
    
    Flags being used in the G_DEFINE_TYPE_EXTENDED sample was "0", so it
    should expand to 0 as well, otherwise the compiler would bark with:
    maman-bar.c: In function ‘maman_bar_get_type’:
    maman-bar.c:36:53: error: ‘flags’ undeclared (first use in this function)
    maman-bar.c:36:53: note: each undeclared identifier is reported only once for each function it appears in
    
    https://bugzilla.gnome.org/show_bug.cgi?id=697250

 gobject/gtype.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gobject/gtype.h b/gobject/gtype.h
index 8a1bff2..f6f6f93 100644
--- a/gobject/gtype.h
+++ b/gobject/gtype.h
@@ -1406,7 +1406,7 @@ guint     g_type_get_type_registration_serial (void);
  *                                        (GClassInitFunc) gtk_gadget_class_intern_init,
  *                                        sizeof (GtkGadget),
  *                                        (GInstanceInitFunc) gtk_gadget_init,
- *                                        (GTypeFlags) flags);
+ *                                        0);
  *       {
  *         const GInterfaceInfo g_implement_interface_info = {
  *           (GInterfaceInitFunc) gtk_gadget_gizmo_init