If we put the emoji filter before the reference filters, each emoji will
have a wrapper element that prevents the reference filter from detecting
the presence of the emoji.

As the emoji filter now runs after the reference filters, references
must contain a literal emoji, not the GitLab Flavored Markdown
versions (:100`, for example).

A weird side-effect is that if you have a label with the 100 emoji, and
a label named :100:, then trying to reference the latter will work (link
to the correct label), but will render with the 100 emoji. I'm
comfortable with that edge case, I think.

Such as those with IDN homographs or embedded
right-to-left (RTLO) characters.

Autolinked hrefs should be escaped

Enable CommonMark source line position information

See merge request gitlab-org/gitlab-ce!23971

The spec needed to be updated because in some cases the resulting
Markdown is slightly different, though equally valid.

including refactoring, disabling sourcepos for pipelines that
don't need it, and minimizing spec changes by disabling
sourcepos when not testing for it explicitly.

This adds 'data-sourcepos' to tags, indicating which
line of markdown it came from.  Sets the stage for
intelligently manipulating specific lines of markdown.

All the ids and classes were stripped.  Add them back in
and make ids unique