Misc fixes

[rtjohnso]

• Fix mkfs bug from use of uninitialized trunk handle.
• Add a flag to the key data structure indicating whether a key is in the database or just a query key. This allows application to use different structures for keys they insert into the db and query keys.
• Optionally return the most recently inserted version of a key as part of a lookup result.
• Change default db file permissions to rw- --- ---.

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