restore acc as required toolset

[SVN r38221]

status/explicit-failures-markup.xml

@@ -23,6 +23,7 @@
     -->
 
     <!-- /////////////// Toolsets /////////////// -->
+    <mark-toolset name="acc" status="required"/>
     <mark-toolset name="borland-5.6.4" status="required"/>
     <mark-toolset name="borland-5.8.2" status="required"/>
     <mark-toolset name="cw-9.4" status="required"/>