As announced in #228, this commit migrates all advisories to the new V2
format, which splits version information into a separate section, and
now has a structure which corresponds to the internal code structure of
the `rustsec` crate.
This is a breaking change for users of `cargo-audit` < 0.9, and anyone
who has written a 3rd party advisory format parser.
As filed, advisory RUSTSEC-2019-0006 simply notes that certain
functions in the covered crate create a "format vulnerability". This
patch, following up on [an exchange of comments on GitHub][1], edits
advisory RUSTSEC-2019-0006 to summarize the risk introduced by a
format vulnerability, copying the wording of the associated advisory
RUSTSEC-2019-0005.
[1]: <https://github.com/RustSec/advisory-db/pull/107#pullrequestreview-250212575>
