This commit reflects changes to clang-format rules. Unfortunately,
these rule changes create a massive change to the codebase, which
causes an apparent rewrite of git history.
Git blame's --ignore-rev flag can be used to ignore this commit when
attempting to `git blame` some code.
This makes PrivateKey store both the key followed by the hash. For
PrivateKeys based on SecretKeys this just means the second half of the
SHA-512 of the seed, and makes a PrivateKey constructed from a SecretKey
give an identical signature to signing directly with sodium.
For derived keys we use a ShortHash of the root key's signing hash
concatenated with the publicly known hash value, so that our derived key
signing hash will be different from the root signing hash and also
different for different derivation parameters.
This also changed one of the asserts in crypto_noop, but upon closer
inspection the copying of the secret key into the signature seems really
wrong, so just changed them to fill with 0s.
