bug#60854: Adjust icons shown with warnings

[Jim Porter <jporterbugs@gmail.com>]

On 1/17/2023 2:19 PM, Kévin Le Gouguec wrote:
> Jim Porter <jporterbugs@gmail.com> writes:
>> Perhaps a bit better would be 🚫, whose official name is apparently "No Entry
>> Sign", even though the slashed circle visual usually just means "No ____",
>> e.g. "No Smoking". Hence, some sources call it the Prohibited emoji.
> 
> (My ¢2: wouldn't a cross mark (❌) also work to convey the idea of
> "suppressing" something?)

That would work too. I still like turning this into a toggle button 
where the icon shows the current state (i.e. is it an active warning - 
⚠️ - or has it been suppressed - ⚬). But changing to 🚫 or ❌ would be 
single-character patches, which is nice too.

> The new icons.el that comes with Emacs 29 would be a prime candidate for
> implementing this, right?  It has the advantage of giving the user some
> degree of control via icon-preference.

Yup, the icon we have today is implemented via icons.el:

  (define-icon warnings-suppress button
     '((emoji "⛔")
       (symbol " ■ ")
       (text " stop "))
     "Suppress warnings."
     :version "29.1"
     :help-echo "Click to suppress this warning type")