Add RC information to patch version strings
Also, fix an issue where Version#to_patch was not returning RCs versions.
This was broken by !139 (merged), my bad! I've added a shared example to ensure that constructors are tested and are common among all issuables.
I discovered this when trying to create a few patch issues (e.g. https://gitlab.com/gitlab-org/gitlab-ce/issues/35357).
Edited by Robert Speicher