Filling paragraphs in m4 mode

[Nikolai Weibull]

Hi!

M4 mode basically has two comments.  One is the dnl variant and one is
the # variant.  Only the # variant is currently handled by the default
fill-paragraph functionality.  How would I go about handling the dnl
variant as well?

(I activate auto-fill-mode with comment-auto-fill-only-comments set in
my prog-mode buffers.)

Thanks!

  Nikolai