Only reopen stdout, stderr, stdin if they haven't already been opened by a redirect

And fix a warning along the way

modules/juce_events/messages/juce_ApplicationBase.cpp

@@ -261,9 +261,13 @@ bool JUCEApplicationBase::initialiseApp()
     if (AttachConsole (ATTACH_PARENT_PROCESS) != 0)
     {
         // if we've launched a GUI app from cmd.exe or PowerShell, we need this to enable printf etc.
-        freopen("CON", "w", stdout);
-        freopen("CON", "w", stderr);
-        freopen("CON", "r", stdin);
+        // However, only reassign stdout, stderr, stdin if they have not been already opened by
+        // a redirect or similar.
+        FILE* ignore;
+
+        if (_fileno(stdout) < 0) freopen_s (&ignore, "CONOUT$", "w", stdout);
+        if (_fileno(stderr) < 0) freopen_s (&ignore, "CONOUT$", "w", stderr);
+        if (_fileno(stdin)  < 0) freopen_s (&ignore, "CONIN$",  "r", stdin);
     }
    #endif