headings class and index php changes, 6.1-sdlc

I have been playing around with the headings class and index php files
to try and make indexing work correctly. I haven't been successful, and
have meade a page that never loads, and times out PHP FPM. I don't
believe this is something as simple as an infinite loop.

ext/6.1-sdlc has also changed, apparently. I'm not sure why, I'm afraid.