v83 release should include library auto-fix logic to help repair user libraries

[GerHobbelt]

Release v82 will have much improved code robustness and has been hardened against invalid/broken/truncated PDF documents appearing anywhere near Qiqqa.

While I've been working on a user library recovery project, one of the lessons learned is that Qiqqa should have more abilities to diagnose and repair or flag-and-repair broken documents and/or metadata in libraries.

As we're currently still binary compatible with v79 (speaking of v82 release here), this implies that a user with some savvy and a v82 install can repair (shared) libraries of any co-workers, which still have v79 or v80 installed on their machines.

Another use would be ease of picking up old research and continuing with what you've collected a couple of years before: Qiqqa v82 can read anything that can be read by v79 (and some older Qiqqa versions)

[GerHobbelt]

Note also the (potential) troubles in S3DB sync reference directories: the s3db SQLite library can be corrupted or otherwise damaged as per #143, for example. Hence we should integrity-check those s3db sync reference libraries as well as the main Qiqqa.library ones!