Added release notes for Review Board 2.5.17.
Review Request #9423 — Created Dec. 4, 2017 and submitted — Latest diff uploaded
This is a small bug fix release that fixes some compatibility problems
with GitLab and LDAP, along with bugs with file attachments and floating
draft banners for replies, e-mail headers, and a query.
Built the docs and looked through them. Checked for spelling and build
errors.