Vendor import libucl 0.9.2

[bofh]

Summary

This patch is just the vendor import. This has not changed anything in the src tree yet.

The release note is available here: https://github.com/vstakhov/libucl/releases/tag/0.9.2

The entire changes from the current version 0.8.0 to 0.9.2 are available here: https://github.com/vstakhov/libucl/compare/0.8.0...0.9.2

[lwhsu]

I would say if it has done the test for merging to main then it's fine. This importing can be seen as the preparation step before updating hits to the contrib/ directory.
BTW, I don't know if that's strictly necessary but I personally prefer to have FREEBSD-upgrade and FREEBSD-Xlist files, for instructions and removing unnecessary files.