[m-rev.] for post-commit review: document the .dep/.dv split

[Julien Fischer]

On Thu, 12 Oct 2023, Zoltan Somogyi wrote:

> Document mmakefile fragment files better.
> 
> compiler/generate_dep_d_files.m:
>     Document the reason for the split between .dep and .dv files.
>
>     Fix typo.
> 
> scripts/mmake.in:
>     Delete code that was only needed for bootstrapping that split
>     (in 1999!).
>
>     Document an incorrect comment.

That's fine.

Julien.