Scripting: Unicode chars in responses are now OK.

This is also relevant to batch scripting.  We need to stay in UTF8 to be safe.
Thanks to Robert Hänggi for reporting this issue.

src/commands/ResponseQueue.h

@@ -48,7 +48,7 @@ class Response {
       std::string mMessage;
    public:
       Response(const wxString &response)
-         : mMessage(response.mb_str())
+         : mMessage(response.utf8_str())
       { }
 
       wxString GetMessage()