Unordered: Small improvements for windows.

[SVN r73760]

test/unordered/swap_tests.cpp

@@ -17,6 +17,10 @@
 #include "../helpers/tracker.hpp"
 #include "../helpers/invariants.hpp"
 
+#if defined(BOOST_MSVC)
+#pragma warning(disable:4127) // conditional expression is constant
+#endif
+
 namespace swap_tests
 {