bug#51041: [External] : bug#51041: 28.0.60; toggle-truncate-lines should not print message

[Drew Adams]

> (toggle-truncate-lines t)
> 
> Prints the message "Truncate long lines enabled". When called from
> elisp, this message should be ignored. If called interactively, the
> message should be displayed.

Yes.

But the right fix is to add "&optional msg",
use (interactive "P\np"), and test for non-nil
MSG as the condition for showing the message.

Lisp code for a command can use that toggle
function, and when _that_ command is invoked
interactively it too might make sense to show
the message (that can depend on the command
and when the toggling occurs as part of it).

The same kind of fix is no doubt appropriate
for some other existing commands that instead
just test `called-interactively-p'.  Surely
we shouldn't perpetuate such design by adding
more such.