fix include guard to not clash with qscriptvalueiterator

Change-Id: Ifb51ed15c93ed68e2a18edd4cda4a921f7e41c34
Reviewed-by: Albert Astals Cid <albert.astals@canonical.com>
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Reviewed-by: Laszlo Papp <lpapp@kde.org>