fix ambiguous assignment in stream wrappers

alib2integrationtest/test-src/testing/TimeoutAqlTest.cpp

@@ -79,8 +79,8 @@ int aqlTest ( int fd_aql, const ext::vector < std::string > & queries, unsigned
 		cli::Environment environment;
 		std::stringstream ss;
-		common::Streams::out = ss;
-		common::Streams::err = ss;
+		common::Streams::out = ext::reference_wrapper < std::ostream > ( ss );
+		common::Streams::err = ext::reference_wrapper < std::ostream > ( ss );
 		// seed cli
 		cli::CharSequence sequence { cli::StringLineInterface ( "set seed " + ext::to_string ( seed ) ) };