QMessageBox/Win: Include detailed text using Ctrl+C to copy

Task-number: QTBUG-21150
Change-Id: I14c214e9f96892f0da4369e7253e363b7313c252
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>

src/widgets/dialogs/qmessagebox.cpp

@@ -1412,7 +1412,10 @@ void QMessageBox::keyPressEvent(QKeyEvent *e)
                 buttonTexts += buttons[i]->text() + QLatin1String("   ");
             }
             textToCopy += buttonTexts + separator;
-
+#ifndef QT_NO_TEXTEDIT
+            if (d->detailsText)
+                textToCopy += d->detailsText->text() + separator;
+#endif
             QApplication::clipboard()->setText(textToCopy);
             return;
         }