Only use std::cout/ cert via Catch::cout/ cert - and make those conditional on CATCH_CONFIG_NOSTDOUT

include/internal/catch_xmlwriter.hpp

@@ -9,9 +9,9 @@
 #define TWOBLUECUBES_CATCH_XMLWRITER_HPP_INCLUDED
 
 #include <sstream>
-#include <iostream>
 #include <string>
 #include <vector>
+#include <catch_stream.h>
 
 namespace Catch {
 
@@ -52,7 +52,7 @@ namespace Catch {
         XmlWriter()
         :   m_tagIsOpen( false ),
             m_needsNewline( false ),
-            m_os( &std::cout )
+            m_os( &Catch::cout() )
         {}
 
         XmlWriter( std::ostream& os )