ob_dump: add -serverside option.
Add BackupEnv implementation suitable for building hot backup.
Implement hot backup atop BackupEnv.
Remove dead code (Miniregion no longer needed with new hot backup impl).
Fix hot backup: wrong signalization of copy/link operation.
Release runtime while performing hot backup.
Ensure files in hot backup have perms 0600.
Remove more dead code.
Merge branch 'rework-hot-backup'