First cut at storing query texts in separate file
Restore serialization
Be smarter about file interlock
Header bump
basebackup notes
Doc updates
Fix serialization bugs
Diff minimization/clean-up
Extent, not offset
Checkpoint garbage collection progress
Checkpoint progress of serialization fix-up
Docs - we garbage collect now
Don't store encoding in key
Style tweak
Remove redundant encoding comment
Clean-up of encoding handling, comments
Comment tweaks, off_t used
Be more frugal with storage for shutdown serialization
Don't repalloc on each buf growth
Correctness bug fix

PGSS_QUERIES_FILE file ought to always be around.

Should follow example of Postgres treatment of relation file extension with
regard to interlock around external ad-hoc file access.