[PATCH REVIEW] libctf: add CTF format specification

[Nick Alcock]

On 26 Oct 2021, Nick Alcock via Binutils told this:

> It's been a long time since most of this was written: it's long past
> time to put it in the binutils source tree.  It's believed correct and
> complete insofar as it goes: it documents format v3 (the current
> version) but not the libctf API or any earlier versions.  (The
> earlier versions can be read by libctf but not generated by it, and you
> are highly unlikely ever to see an example of any of them.)

Ping? any comments? I'll commit this in about a day if nobody says
anything.

(It's mostly the bumped-up makeinfo version I'm concerned about, but
we don't abort if that's not set, we just skip doc generation, so
presumably this is fine?)