Follow-up of T284883: CodeMirror – support highlighting the new <tvar> tag syntax.

Steps to replicate the issue:

Open the 2010 Wikitext Editor, CodeMirror enabled, and type the following content:

<translate>
[[<tvar name=foo>foo</tvar>|bar]]
</translate>

What happens?:
The foo tvar is not parsed as a tvar, only as an internal link target.

What should have happened instead?:
Ideally, the highlighter should mix tvar style and link target style, e.g. bolding the tvar tag name.