I'm assuming that it's fine if a _const_ or _pure_ function
calls assert. It is assumed that the assert won't trigger,
and even if it does, it can only trigger on the first call
with a given set of parameters, and we don't care if the
compiler moves the order of calls.
This adds forward-secure authentication of journal files. This patch
includes key generation as well as tagging of journal files,
Verification of journal files will be added in a later patch.
