This parser can be reused for other purposes. It's inspired by
https://bitheap.org/cram/
Although eelco's impostor exists https://github.com/mobusoperandi/eelco,
it is not very nice to depend on out of tree testing frameworks with no
way to customize them.
Change-Id: Ifca50177e09730182baf0ebf829c3505bbb0274a