Enhance documentation of Fl_Menu_Item::value().

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@10282 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

FL/Fl_Menu_Item.H

@@ -305,7 +305,13 @@ struct FL_EXPORT Fl_Menu_Item {
     radio() false, or by an item with FL_MENU_DIVIDER turned on.
   */
   int radio() const {return flags&FL_MENU_RADIO;}
-  /** Returns the current value of the check or radio item. */
+  /** Returns the current value of the check or radio item.
+      This is zero (0) if the menu item is not checked and
+      non-zero otherwise. You should not rely on a particular value,
+      only zero or non-zero.
+      \note The returned value for a checked menu item as of FLTK 1.3.2
+      is FL_MENU_VALUE (4), but may be 1 in a future version.
+  */
   int value() const {return flags&FL_MENU_VALUE;}
   /**
     Turns the check or radio item "on" for the menu item. Note that this