Boost.Chrono: Set vacpp as unusable and try again with pathscale

[SVN r68405]

status/explicit-failures-markup.xml

@@ -481,8 +481,8 @@
     <!-- chrono -->
     <library name="chrono">
         <mark-unusable>
-            <toolset name="borland-*"/>
-            <toolset name="pathscale*"/>
+            <toolset name="borland"/>
+            <toolset name="vacpp"/>
             <note author="Vicente J. Botet Escriba">
                 The compiler does not support features that are essential for the library.
             </note>