Hi,

I'm happy to finally be able to send an updated version of this patch
that touches most backends in lisp/, but not the manual.  I have been
moving over the summer etc.

You now specify unnumbered headlines with properties.  I think this is
better since being unnumbered it's a pretty permanent state.  It's
pretty hard to discover though, other than by looking at the output.

So this works as expected:

* Some headline
  :PROPERTIES:
  :UNNUMBERED: t
  :END:

There's no :NUMBERED property and :UNNUMBERED is hardcoded.

I introduce a new function `org-export-get-headline-id` which returns
the first non-nil from the following list.  There's a caveat:
CUSTOM_ID is ensured to be unique!  Did I open the famous can of worm?

1. The CUSTOM_ID property.
2. A relative level number if the headline is numbered.
3. The ID property
4. A new generated unique ID.

Anyhow, `org-export-get-headline-id' ensures that we can refer to
unnumbered headlines, which was not possible before.  Of course, in
LaTeX such ref to a \section* will be nonsense, so we could introduce
a \pageref here.  I'm unsure about whether this conflicts
`org-latex-custom-id-as-label' which I had never seen until today
(also notes on this in patch).

I have updated backends in lisp/, but I'm at most(!) an "expert" on
LaTeX.  However, I have tested all backends to the best of my ability.

Please feel free to test and let me know about any discrepancies!

Cheers,
Rasmus

PS: Not knowing or caring much about md, the links generated by it to
headlines seem wrong.  Referring to headline 1 it only prints "1".
Should it be something like "[LABEL](1)"?


-- 
This is the kind of tedious nonsense up with which I will not put