[m-rev.] for review: rename the .ll_debug grade component for hlc grades to .c_debug

[Peter Wang]

On Tue, 20 Dec 2022 22:41:25 +1100 "Zoltan Somogyi" <zoltan.somogyi at runbox.com> wrote:
> For review by anyone.
> 
> I am particularly seeking opinions on the XXX in the log file:
> the treatment of the --c-debug option to mgnuc.

It's pretty confusing.

Looking at the thread that prompted this change,
I don't really see how renaming .ll_debug to .c_debug helps.

How about renaming .ll_debug to .rt_debug, .debug_runtime,
or something like that?

Peter