Fixed err:XS0088 per a suggestion from Achim

xproc/src/main/xml/specification.xml

@@ -3040,7 +3040,7 @@ Variable names are always expressed as
       <error code="S0088">It is
       a <glossterm>static error</glossterm> if the qualified name of a static option
       <glossterm baseform="shadow">shadows</glossterm>
-      the name of another static option.</error></para>
+      the name of another static option or a variable.</error></para>
 
       <para>It is not an error if two static options with the same name appear
       in different scopes, but it is not good practice. Bear in mind, for