Locale Nesting Audit

Audit the key structure of a locale file against a contract the caller states. Reports a message that is also the prefix of another message, which a loader nesting on the separator cannot hold both of so it keeps one and drops the other; two keys differing only in case, which is two keys to the file and one to any case-insensitive platform; a doubled separator, which resolves to a different key than written; and whitespace in a key, which several loaders trim or reject.