[boost] [type_traits][docs] example for is_base_of<> needs to be updated

documentation for is_base_of says: "... Note that is_base_of<X,X> will always inherit from true_type..." and few lines after: "is_base_of<Base, Base>::value is an integral constant expression that evaluates to false: a class is not it's own base.", http://boost.org/doc/html/boost_typetraits/reference.html#boost_typetraits.i... -- Pavel Kalugin