new command-line option -nextgc-factor

[<don...@is...>]

Bruno Haible writes:

 > For debugging GC problems, I have added a new option -nextgc-factor.
 > It is a factor that gets applied to the amount of space that can be
 > consumed before the next GC is triggered.
...
 > I don't want to document this option, because the default GC frequency
 > is completely sufficient for the average user.

You do have a section on debugging (also gc) in impnotes.
Why not include what you wrote in this message there?
And in the doc for command line arguments refer to
the appropriate section of impnotes.