Use a local copy of is_same trait.

boost::core::is_same is deprecated, so use a local copy to avoid adding
a dependency on Boost.TypeTraits. Use Boost.TypeTraits in tests.

Also added a missing include.

include/boost/bind/bind.hpp

@@ -22,7 +22,6 @@
 //
 
 #include <boost/config.hpp>
-#include <boost/ref.hpp>
 #include <boost/bind/mem_fn.hpp>
 #include <boost/type.hpp>
 #include <boost/is_placeholder.hpp>
@@ -31,8 +30,9 @@
 #include <boost/bind/std_placeholders.hpp>
 #include <boost/detail/workaround.hpp>
 #include <boost/visit_each.hpp>
+#include <boost/core/ref.hpp>
 #include <boost/core/enable_if.hpp>
-#include <boost/core/is_same.hpp>
+#include <boost/bind/detail/is_same.hpp>
 
 #if !defined( BOOST_NO_CXX11_RVALUE_REFERENCES )
 #include <utility> // std::forward