[m-rev.] for review: require module a.b to be a.b.m without mmc -f

[Julien Fischer]

On Sun, 12 Jan 2020, Zoltan Somogyi wrote:

> For review, and maybe a tryout, by Julien or Peter.
>
> There should also be an announcement, such as:
>
> The compiler now requires that, in projects that do not build
> a Mercury.modules file using e.g. "mmc -f *.m", submodules must be stored
> in files whose name is the fully qualified module name followed by ".m".
> This means that e.g. a module named a.b.c must be in a file named
> a.b.c.m.

It might be nice to include a brief explanation of *why* this change
has been made.

> However, I don't know where to put this during the release process.

In the NEWS file on the master branch, in the section named
"Changes that may break compatibility".

Note that I will merge this on to the release branch once it has been
committed and tested on the master branch.

I will take a look at the rest of the change this evening.

Julien.