[PATCH 1/3] mime node: Record depth-first part numbers

[Austin Clements]

Quoth myself on Jan 18 at  9:12 pm:
> Quoth Jani Nikula on Jan 19 at 12:25 am:
> > FWIW, I'm not a big fan of casting away const. Either it is const, or it
> > isn't. Not very many places would be affected if you dropped the const
> > qualifier from the related interface(s) altogether, and things would
> > look cleaner here. But I suppose this is a matter of taste.
> 
> I'm not particularly happy with this either.  Unfortunately, dropping
> the const here affects a surprising number of places, including the
> entire MIME node API.

I've changed my mind and removed a few consts so that this funny cast
isn't necessary.  (It also turned out that when I tried this before,
I'd given up just a smidgen before removing enough consts to make it
work.)

> I think that, at a deep level, depth-first numbering simply doesn't
> resonate with an extremely hierarchical API like this and that
> dissonance is going to have to focus somewhere.  There have been
> discussions of switching to hierarchical part numbering before (in
> particular, because depth-first numbering is unstable with encrypted
> parts) and I'll probably restart those after all of this is done.

I have not, however, changed my mind about this.