Boost.Ratio: Mark Borland compiler as unusable

[SVN r67648]

status/explicit-failures-markup.xml

@@ -4444,6 +4444,13 @@ for more information.
         </mark-expected-failures>
     </library>
 
+    <!-- ratio -->
+    <library name="ratio">
+      <mark-unusable>
+        <toolset name="borland-*"/>
+      </mark-unusable>
+    </library>
+
     <!-- regex -->
     <library name="regex">
         <test name="regex_token_iterator_eg_2">