Not enough theme functions

I wanted to change the main glossary page to include a link to add a glossary term (this is a hard-coded link to a webform via the webforms module). So I went into the module, as usual, to look for the appropriate theme function to override. To my shock I found there wasn't one - there was only a hard-coded function that spews output to the end of the $output variable! I was presented with two options here: hack the module to output the code I wanted, or re-write the main page as a theme function, so that it could be overridden. I have done the latter, and attach my changes to 5.x-2.6.

Incorporate these into the latest version, or not, whatever. These changes should help people to theme glossary pages the way they want, rather than how the module decides it wants to display things. Separation of markup and content.