re-enabled testing intrusive on sun

[SVN r56120]

status/explicit-failures-markup.xml

@@ -1883,7 +1883,6 @@
     <library name="intrusive">
         <mark-unusable>
             <toolset name="borland-5.*"/>
-            <toolset name="sun-5.*"/>
             <toolset name="msvc-6.5*"/>
             <toolset name="cw-9.*"/>
             <toolset name="gcc-2.95*"/>