Mention that not all standard IDs are stock IDs.

Also add a link to the list of stock IDs from the standard IDs documentation.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65369 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/defs.h

@@ -198,7 +198,13 @@ enum wxBackgroundStyle
 
 
 /**
-    Standard menu IDs.
+    Standard IDs.
+
+    Notice that some, but @em not all, of these IDs are also stock IDs, i.e.
+    you can use them for the button or menu items without specifying the label
+    which will be provided by the underlying platform itself. See @ref "the
+    list of stock items" for the subset of standard IDs which are stock IDs as
+    well.
 */
 enum wxStandardID
 {