Remove unused get_offsets functions from headers

gdk/gdkinternals.h

@@ -326,10 +326,6 @@ extern const GOptionEntry _gdk_windowing_args[];
 gchar *_gdk_windowing_substitute_screen_number (const gchar *display_name,
                                                 gint         screen_number);
 
-void     _gdk_windowing_window_get_offsets      (GdkWindow  *window,
-                                                 gint       *x_offset,
-                                                 gint       *y_offset);
-
 void _gdk_windowing_got_event                (GdkDisplay       *display,
                                               GList            *event_link,
                                               GdkEvent         *event,

gdk/win32/gdkprivate-win32.h

@@ -167,9 +167,6 @@ void _gdk_win32_window_move_region (GdkWindow       *window,
 				    const cairo_region_t *region,
 				    gint             dx,
 				    gint             dy);
-void _gdk_win32_windowing_window_get_offsets (GdkWindow *window,
-					      gint      *x_offset,
-					      gint      *y_offset);
 
 
 void _gdk_win32_selection_init (void);

gdk/x11/gdkwindow-x11.h

@@ -163,9 +163,6 @@ void            _gdk_x11_window_tmp_unset_parent_bg (GdkWindow *window);
 void            _gdk_x11_window_tmp_reset_parent_bg (GdkWindow *window);
 
 GdkCursor      *_gdk_x11_window_get_cursor          (GdkWindow *window);
-void            _gdk_x11_window_get_offsets         (GdkWindow *window,
-                                                     gint      *x_offset,
-                                                     gint      *y_offset);
 
 void            _gdk_x11_window_update_size         (GdkWindowImplX11 *impl);