[glib] G_DECLARE_DERIVED_TYPE: allow forward declarations

[Ryan Lortie <desrt src gnome org>]

commit f3c604d2735fd63c5d45ecbeff9cb0e90d3356ac
Author: Christian Hergert <christian hergert me>
Date:   Tue Jan 27 18:50:04 2015 +0000

    G_DECLARE_DERIVED_TYPE: allow forward declarations
    
    This allows multiple declarations such as:
    
     typedef struct _Foo Foo;
    
    as is needed when you have systems with circular referencing.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=743596

 gobject/gtype.h |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/gobject/gtype.h b/gobject/gtype.h
index 6f3f808..3dc3d9c 100644
--- a/gobject/gtype.h
+++ b/gobject/gtype.h
@@ -1464,8 +1464,9 @@ guint     g_type_get_type_registration_serial (void);
  **/
 #define G_DECLARE_DERIVABLE_TYPE(ModuleObjName, module_obj_name, MODULE, OBJ_NAME, ParentName) \
   GType module_obj_name##_get_type (void);                                                               \
-  typedef struct { ParentName parent_instance; } ModuleObjName;                                          \
+  typedef struct _##ModuleObjName ModuleObjName;                                                         \
   typedef struct _##ModuleObjName##Class ModuleObjName##Class;                                           \
+  struct _##ModuleObjName { ParentName parent_instance; };                                               \
                                                                                                          \
   static inline ModuleObjName * MODULE##_##OBJ_NAME (gpointer ptr) {                                     \
     return G_TYPE_CHECK_INSTANCE_CAST (ptr, module_obj_name##_get_type (), ModuleObjName); }             \