eliminate unnecessary workaround for modern msvc versions

include/boost/mpl/has_xxx.hpp

@@ -155,10 +155,10 @@ template<> struct trait<T> \
 // SFINAE-based implementations below are derived from a USENET newsgroup's 
 // posting by Rani Sharoni (comp.lang.c++.moderated, 2002-03-17 07:45:09 PST)
 
-#   elif BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1400)) \
+#   elif BOOST_WORKAROUND(BOOST_MSVC, <= 1400) \
       || BOOST_WORKAROUND(__IBMCPP__, <= 700)
 
-// MSVC 7.1+ & VACPP
+// MSVC 7.1 & MSVC 8.0 & VACPP
 
 // agurt, 15/jun/05: replace overload-based SFINAE implementation with SFINAE
 // applied to partial specialization to fix some apparently random failures