Fix TR1 markup: toolset name change.

[SVN r34137]

status/explicit-failures-markup.xml

@@ -3954,6 +3954,7 @@ for more information.
         <mark-unusable>
             <toolset name="msvc"/>
             <toolset name="VC6*"/>
+            <toolset name="vc-6*"/>
             <note author="John Maddock">
                 VC6 has a buggy using declaration syntax which
                 basically makes it impossible to implement the