Retain heading HTML in <a section> links.

No need for this here.  The `<willbelink>` hack is only needed if you're building a string of HTML, like the TOC code is, and need to trick the parser into (temporarily) accepting nested <a>s before you clean up.

Since you're instead parsing the contents by themselves and *then* inserting them into the <a> container, you're fine.  See the next line notes, though...