bug#60854: Adjust icons shown with warnings

[Jim Porter <jporterbugs@gmail.com>]

On 1/16/2023 1:58 AM, Daniel Martín via Bug reports for GNU Emacs, the 
Swiss army knife of text editors wrote:
> Pedro Andres Aranda Gutierrez <paaguti@gmail.com> writes:
> 
>> Currently, warnings are visually "enhanced" with a ⛔ sign.
>> However, the warning signs are ⚠️ or its slightly different European
>> version.
> 
> I had the same question as you, but it turns out that the ⛔ icon is not
> intended to represent a warning, it is a button that you can click to
> *suppress* that warning type.

I think the confusion is that the literal meaning of the ⛔ icon is "No 
Entry", so it's very easy to read it as, "Stop! Don't go this way 
because there's a problem ahead."

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.

Another way to handle the UI (which I see more often, and personally 
prefer) is that the button is a toggle, and its icon indicates the 
current state. This would require adding a bit of code so that clicking 
the button again *un*suppresses the warning, but then you could use 
something like ⚠️ to indicate that the warning is currently enabled (and 
clicking it will suppress it), and maybe ⚪ or ⚬ to indicate that the 
warning is currently suppressed (and clicking it will reenable it). Or 
maybe ❗ and ❕, respectively?

We could also add actual images for this icon if none of these are quite 
right, and use the emoji as a fallback.