gitlab: Upgrade to 8.8
- GitLab Software + patches ported to GitLab 8.8.7;
- Configs synced with upstream and SlapOS-ified;
- Fix promises due to curl upgrade
Demo instance: https://softinst69126.host.vifib.net/
@jerome @kazuhiko @kirr: I verified promises, patches, and so on as expected, but please have a look in case I would have missed something.
PS: no change are made in gitlab-workhorse and gitlab-shell upstream this time, but Nexedi patches and a cherry-picked commit are applied in a merge request on gitlab-ce.