bug#48724: Code collapsing and outline headings for elisp

[Juri Linkov <juri@linkov.net>]

> Serious problem is that the two important variables: `outline-regexp' and
> `outline-heading-alist' are not customizable by using "M-x customize-group".
>
> Additionally both of them should be customizable per mode.  Don't you think so?

I think that modes should set `outline-regexp' and `outline-heading-alist'
according to the constructs of their programming language.  Then users
don't need to customize these variables.

> There has been a discussion today about outline-minor-mode settings for fortran
> (both fixed and free form).  Have had a go at using "!" and "!!", but "Hide Body"
> did not hide the body.
>
> There could be some default headings for fortran when outline-minor-mode is enabled.
> One could follow the current setup for emacs-lisp-mode, for fortran.
>
> !! for heading level 1
> !!! for subheading level 2
> !!!! for subsubheading level 3

I agree it would be nice to set an appropriate value of `outline-regexp'
and `outline-heading-alist' for fortran-mode in lisp/progmodes/fortran.el.

But the last time I used Fortran was when Fortran had the "C" character
for comments at the first fixed column on a punched card, and now
your example uses some new syntax "!" for comments, so sorry, can't help here.

This task would be a nice assignment for the group of students.