fix compilation error on release mode

Text.cpp

@@ -24,6 +24,10 @@ FlushingOStream::FlushingOStream(DynamicBuffer* buffer)
     : std::ostream(buffer)
 {}
 
+FlushingOStream::FlushingOStream(const Framework::FlushingOStream& stream)
+    : std::ostream(stream.rdbuf())
+{}
+
 FlushingOStream::~FlushingOStream()
 {
     flush();

Text.h

@@ -26,6 +26,7 @@ namespace Framework
     {
     public:
         DLLEXPORT FlushingOStream(DynamicBuffer* buffer);
+        DLLEXPORT FlushingOStream(const Framework::FlushingOStream& stream);
 
         DLLEXPORT ~FlushingOStream();
     };