Define a :gl: Sphinx role that takes a GitLab issue/MR number as an
argument and creates a hyperlink to the relevant ISC GitLab URL. This
makes it easy to reach ISC GitLab pages directly from the release notes.
Make all GitLab references in the release notes use the new Sphinx role.
The release notes were previously built as a separate document
(including the PDF version). It was agreed that this doesn't make much
sense, so the release notes are now included only as an appendix to the
BIND 9 ARM.
The ARM and the manpages have been converted into Sphinx documentation
format.
Sphinx uses reStructuredText as its markup language, and many of its
strengths come from the power and straightforwardness of
reStructuredText and its parsing and translating suite, the Docutils.
