bug#33939: 26.1; Avoid loading libs eagerly or unnecessarily in mhtml-mode/sgml-mode

[Eli Zaretskii]

> From:  Leo Liu <sdl.web@gmail.com>
> Cc: 33939@debbugs.gnu.org
> Date: Tue, 08 Jan 2019 06:43:20 +0800
> 
> On 2019-01-07 21:56 +0200, Eli Zaretskii wrote:
> > This is OK for the emacs-26 branch, thanks.
> 
> I was bored enough to check if js.el had any low-hanging fruits and
> found another one. js.el uses nothing from thingatpt since
> forward-symbol now lives in subr.el. Should I go ahead and put the
> following patch on emacs-26?

If this causes a significant slowdown of loading, yes, please.  If the
slowdown is not significant, please do this on master.

Thanks.

> Sorry to discover these issues one after another.

No need to be sorry, thanks for looking at these issues.