xtb 6.7.2

[Albkat]

This is the general issue to track the next xtb release (6.7.2).

This release is intended to be the final xtb release based on the old infrastructure and is therefore expected to be as stable as possible. Most development efforts for this release have been focused on the build process. However, please feel free to add any critical issues that should be addressed.

[marcelmbn]

Added some sub-issues that are relevant for the 6.7.2 release IMHO.