Fix non-standard test feature test collection. I.e. make the feature

collection no rely on implementioned defined behaviour. And fix check
program handling of no-expression invocations vs expression invocations.

include/boost/predef/platform.h

@@ -1,13 +1,15 @@
 /*
-Copyright Rene Rivera 2013
+Copyright Rene Rivera 2013-2015
 Copyright (c) Microsoft Corporation 2014
 Distributed under the Boost Software License, Version 1.0.
 (See accompanying file LICENSE_1_0.txt or copy at
 http://www.boost.org/LICENSE_1_0.txt)
 */
 
+#if !defined(BOOST_PREDEF_PLATFORM_H) || defined(BOOST_PREDEF_INTERNAL_GENERATE_TESTS)
 #ifndef BOOST_PREDEF_PLATFORM_H
 #define BOOST_PREDEF_PLATFORM_H
+#endif
 
 #include <boost/predef/platform/mingw.h>
 #include <boost/predef/platform/windows_desktop.h>