docs: Add private structures to private sections

docs/reference/gtk/gtk3-sections.txt

@@ -419,6 +419,7 @@ GTK_ASPECT_FRAME_CLASS
 GTK_IS_ASPECT_FRAME_CLASS
 GTK_ASPECT_FRAME_GET_CLASS
 <SUBSECTION Private>
+GtkAspectFramePrivate
 gtk_aspect_frame_get_type
 </SECTION>
 
@@ -439,6 +440,7 @@ GTK_BUTTON_BOX_CLASS
 GTK_IS_BUTTON_BOX_CLASS
 GTK_BUTTON_BOX_GET_CLASS
 <SUBSECTION Private>
+GtkButtonBoxPrivate
 gtk_button_box_get_type
 </SECTION>
 
@@ -455,6 +457,7 @@ GTK_BIN_CLASS
 GTK_IS_BIN_CLASS
 GTK_BIN_GET_CLASS
 <SUBSECTION Private>
+GtkBinPrivate
 gtk_bin_get_type
 </SECTION>
 
@@ -480,6 +483,7 @@ GTK_BOX_CLASS
 GTK_IS_BOX_CLASS
 GTK_BOX_GET_CLASS
 <SUBSECTION Private>
+GtkBoxPrivate
 gtk_box_get_type
 </SECTION>
 
@@ -665,6 +669,7 @@ GTK_CHECK_MENU_ITEM_CLASS
 GTK_IS_CHECK_MENU_ITEM_CLASS
 GTK_CHECK_MENU_ITEM_GET_CLASS
 <SUBSECTION Private>
+GtkCheckMenuItemPrivate
 gtk_check_menu_item_get_type
 </SECTION>
 
@@ -717,6 +722,7 @@ GTK_IS_HSV
 GTK_IS_HSV_CLASS
 GTK_HSV_GET_CLASS
 <SUBSECTION Private>
+GtkHSVPrivate
 gtk_hsv_get_type
 </SECTION>
 
@@ -755,6 +761,7 @@ GTK_COLOR_SELECTION_CLASS
 GTK_IS_COLOR_SELECTION_CLASS
 GTK_COLOR_SELECTION_GET_CLASS
 <SUBSECTION Private>
+GtkColorSelectionPrivate
 gtk_color_selection_get_type
 </SECTION>
 
@@ -772,6 +779,7 @@ GTK_COLOR_SELECTION_DIALOG_CLASS
 GTK_IS_COLOR_SELECTION_DIALOG_CLASS
 GTK_COLOR_SELECTION_DIALOG_GET_CLASS
 <SUBSECTION Private>
+GtkColorSelectionDialogPrivate
 gtk_color_selection_dialog_get_type
 </SECTION>
 
@@ -901,6 +909,7 @@ GTK_CONTAINER_CLASS
 GTK_IS_CONTAINER_CLASS
 GTK_CONTAINER_GET_CLASS
 <SUBSECTION Private>
+GtkContainerPrivate
 gtk_container_get_type
 </SECTION>
 
@@ -936,6 +945,7 @@ GTK_DIALOG_CLASS
 GTK_IS_DIALOG_CLASS
 GTK_DIALOG_GET_CLASS
 <SUBSECTION Private>
+GtkDialogPrivate
 gtk_dialog_get_type
 </SECTION>
 
@@ -1361,6 +1371,7 @@ GTK_FIXED_CLASS
 GTK_IS_FIXED_CLASS
 GTK_FIXED_GET_CLASS
 <SUBSECTION Private>
+GtkFixedPrivate
 GtkFixedChild
 gtk_fixed_get_type
 </SECTION>
@@ -1421,6 +1432,7 @@ GTK_FONT_SELECTION_CLASS
 GTK_IS_FONT_SELECTION_CLASS
 GTK_FONT_SELECTION_GET_CLASS
 <SUBSECTION Private>
+GtkFontSelectionPrivate
 gtk_font_selection_get_type
 </SECTION>
 
@@ -1445,6 +1457,7 @@ GTK_FONT_SELECTION_DIALOG_CLASS
 GTK_IS_FONT_SELECTION_DIALOG_CLASS
 GTK_FONT_SELECTION_DIALOG_GET_CLASS
 <SUBSECTION Private>
+GtkFontSelectionDialogPrivate
 gtk_font_selection_dialog_get_type
 </SECTION>
 
@@ -1469,6 +1482,7 @@ GTK_FRAME_CLASS
 GTK_IS_FRAME_CLASS
 GTK_FRAME_GET_CLASS
 <SUBSECTION Private>
+GtkFramePrivate
 gtk_frame_get_type
 </SECTION>
 
@@ -1492,6 +1506,7 @@ GTK_HANDLE_BOX_CLASS
 GTK_IS_HANDLE_BOX_CLASS
 GTK_HANDLE_BOX_GET_CLASS
 <SUBSECTION Private>
+GtkHandleBoxPrivate
 gtk_handle_box_get_type
 </SECTION>
 
@@ -1726,6 +1741,7 @@ GTK_IMAGE_CLASS
 GTK_IS_IMAGE_CLASS
 GTK_IMAGE_GET_CLASS
 <SUBSECTION Private>
+GtkImagePrivate
 gtk_image_get_type
 GtkImageIconSetData
 GtkImageImageData
@@ -1761,6 +1777,7 @@ GTK_IS_IMAGE_MENU_ITEM
 GTK_IS_IMAGE_MENU_ITEM_CLASS
 GTK_TYPE_IMAGE_MENU_ITEM
 <SUBSECTION Private>
+GtkImageMenuItemPrivate
 gtk_image_menu_item_get_type
 </SECTION>
 
@@ -1807,6 +1824,7 @@ GTK_IM_CONTEXT_SIMPLE_CLASS
 GTK_IS_IM_CONTEXT_SIMPLE_CLASS
 GTK_IM_CONTEXT_SIMPLE_GET_CLASS
 <SUBSECTION Private>
+GtkIMContextSimplePrivate
 gtk_im_context_simple_get_type
 </SECTION>
 
@@ -1847,6 +1865,7 @@ GTK_IS_INVISIBLE_CLASS
 GTK_INVISIBLE_GET_CLASS
 <SUBSECTION Private>
 gtk_invisible_get_type
+GtkInvisiblePrivate
 </SECTION>
 
 <SECTION>
@@ -1906,6 +1925,7 @@ GTK_IS_LABEL_CLASS
 GTK_LABEL_GET_CLASS
 <SUBSECTION Private>
 gtk_label_get_type
+GtkLabelPrivate
 GtkLabelSelectionInfo
 </SECTION>
 
@@ -1931,6 +1951,7 @@ GTK_LAYOUT_CLASS
 GTK_IS_LAYOUT_CLASS
 GTK_LAYOUT_GET_CLASS
 <SUBSECTION Private>
+GtkLayoutPrivate
 gtk_layout_get_type
 </SECTION>
 
@@ -2468,6 +2489,7 @@ GTK_IS_RANGE_CLASS
 GTK_RANGE_GET_CLASS
 <SUBSECTION Private>
 gtk_range_get_type
+GtkRangePrivate
 GtkRangeLayout
 GtkRangeStepTimer
 </SECTION>
@@ -2841,6 +2863,7 @@ GTK_IS_SCROLLED_WINDOW_CLASS
 GTK_SCROLLED_WINDOW_GET_CLASS
 <SUBSECTION Private>
 gtk_scrolled_window_get_type
+GtkScrolledWindowPrivate
 </SECTION>
 
 <SECTION>
@@ -2857,6 +2880,7 @@ GTK_IS_SEPARATOR_CLASS
 GTK_SEPARATOR_GET_CLASS
 <SUBSECTION Private>
 gtk_separator_get_type
+GtkSeparatorPrivate
 </SECTION>
 
 <SECTION>
@@ -3554,6 +3578,7 @@ GTK_IS_TOGGLE_BUTTON_CLASS
 GTK_TOGGLE_BUTTON_GET_CLASS
 <SUBSECTION Private>
 gtk_toggle_button_get_type
+GtkToggleButtonPrivate
 </SECTION>
 
 <SECTION>
@@ -4426,6 +4451,7 @@ GTK_CELL_RENDERER_CLASS
 GTK_IS_CELL_RENDERER_CLASS
 GTK_CELL_RENDERER_GET_CLASS
 <SUBSECTION Private>
+GtkCellRendererPrivate
 gtk_cell_renderer_get_type
 </SECTION>
 
@@ -4461,6 +4487,7 @@ GTK_IS_CELL_RENDERER_COMBO_CLASS
 GTK_CELL_RENDERER_COMBO_GET_CLASS
 <SUBSECTION Private>
 gtk_cell_renderer_combo_get_type
+GtkCellRendererComboPrivate
 </SECTION>
 
 <SECTION>
@@ -4511,6 +4538,7 @@ GTK_IS_CELL_RENDERER_PIXBUF_CLASS
 GTK_CELL_RENDERER_PIXBUF_GET_CLASS
 <SUBSECTION Private>
 gtk_cell_renderer_pixbuf_get_type
+GtkCellRendererPixbufPrivate
 </SECTION>
 
 <SECTION>
@@ -4528,6 +4556,7 @@ GTK_IS_CELL_RENDERER_TEXT_CLASS
 GTK_CELL_RENDERER_TEXT_GET_CLASS
 <SUBSECTION Private>
 gtk_cell_renderer_text_get_type
+GtkCellRendererTextPrivate
 </SECTION>
 
 <SECTION>
@@ -4551,6 +4580,7 @@ GTK_IS_CELL_RENDERER_TOGGLE_CLASS
 GTK_CELL_RENDERER_TOGGLE_GET_CLASS
 <SUBSECTION Private>
 gtk_cell_renderer_toggle_get_type
+GtkCellRendererTogglePrivate
 </SECTION>
 
 <SECTION>
@@ -4586,6 +4616,7 @@ GTK_IS_CELL_RENDERER_ACCEL_CLASS
 GTK_CELL_RENDERER_ACCEL_GET_CLASS
 <SUBSECTION Private>
 gtk_cell_renderer_accel_get_type
+GtkCellRendererAccelPrivate
 </SECTION>
 
 <SECTION>
@@ -5819,6 +5850,7 @@ GTK_IS_ICON_FACTORY_CLASS
 GTK_TYPE_ICON_SET
 GTK_TYPE_ICON_SOURCE
 <SUBSECTION Private>
+GtkIconFactoryPrivate
 gtk_icon_factory_get_type
 gtk_icon_set_get_type
 gtk_icon_source_get_type