Version 1.51.3

- This release was made from an earlier state of master, before a breaking
  change was merged, while we decide whether to revert that change or not.

- Closed bugs and merge requests:

  * CI improvements on GitLab [!14, !15, !19, Claudio André]
  * Fix CI build on Ubuntu [#16, !18, !21, Claudio André, Philip Chimento]
This tag has no release notes.