docs: enum cleanup

Move GtkArrowPlacement to the GtkMenu docs. This type is
only used for a style property there.

docs/reference/gtk/gtk3-sections.txt

@@ -2183,6 +2183,7 @@ gtk_link_button_get_type
 <FILE>gtkmenu</FILE>
 <TITLE>GtkMenu</TITLE>
 GtkMenu
+GtkArrowPlacement
 gtk_menu_new
 gtk_menu_new_from_model
 gtk_menu_set_screen
@@ -6505,7 +6506,6 @@ gtk_binding_set_add_path
 <SECTION>
 <FILE>gtkenums</FILE>
 <TITLE>Standard Enumerations</TITLE>
-GtkArrowPlacement
 GtkArrowType
 GtkAttachOptions
 GtkBaselinePosition

gtk/gtkenums.h

@@ -79,22 +79,6 @@ typedef enum
   GTK_ALIGN_BASELINE
 } GtkAlign;
 
-
-/**
- * GtkArrowPlacement:
- * @GTK_ARROWS_BOTH: Place one arrow on each end of the menu.
- * @GTK_ARROWS_START: Place both arrows at the top of the menu.
- * @GTK_ARROWS_END: Place both arrows at the bottom of the menu.
- *
- * Used to specify the placement of scroll arrows in scrolling menus.
- */
-typedef enum
-{
-  GTK_ARROWS_BOTH,
-  GTK_ARROWS_START,
-  GTK_ARROWS_END
-} GtkArrowPlacement;
-
 /**
  * GtkArrowType:
  * @GTK_ARROW_UP: Represents an upward pointing arrow.

gtk/gtkmenu.h

@@ -48,6 +48,21 @@ typedef struct _GtkMenu        GtkMenu;
 typedef struct _GtkMenuClass   GtkMenuClass;
 typedef struct _GtkMenuPrivate GtkMenuPrivate;
 
+/**
+ * GtkArrowPlacement:
+ * @GTK_ARROWS_BOTH: Place one arrow on each end of the menu.
+ * @GTK_ARROWS_START: Place both arrows at the top of the menu.
+ * @GTK_ARROWS_END: Place both arrows at the bottom of the menu.
+ *
+ * Used to specify the placement of scroll arrows in scrolling menus.
+ */
+typedef enum
+{
+  GTK_ARROWS_BOTH,
+  GTK_ARROWS_START,
+  GTK_ARROWS_END
+} GtkArrowPlacement;
+
 /**
  * GtkMenuPositionFunc:
  * @menu: a #GtkMenu.