bug#62677: 30.0.50; Need to find a better name for flyspell-prog-mode

[Juri Linkov]

> Here's the plan I'd propose: Add a new defvar-local
> `flyspell-use-prog-mode' or somesuch that major modes can set.  Now,
> when a user enables `flymake-mode' in a buffer where that variable is
> non-nil, the extra stuff done in `flyspell-prog-mode' gets done too.
> Then decide which built-in major modes that would benefit, and set that
> variable in them.
>
> Would `prog-mode' be a candidate though, or do we expect any modes
> inheriting from it to want the regular `flyspell-mode'?

Removing flyspell-prog-mode will break a lot of user configs
that often contain such a pair:

  (add-hook 'text-mode-hook 'flyspell-mode)
  (add-hook 'prog-mode-hook 'flyspell-prog-mode)