Add unit test for oox::TokenMap

Change-Id: Iced083868a84fd9fbb97ad91dfc0acbf5b69b766
Reviewed-on: https://gerrit.libreoffice.org/11559
Reviewed-by: David Ostrovsky <David.Ostrovsky@gmx.de>
Tested-by: David Ostrovsky <David.Ostrovsky@gmx.de>