bug#28194: text-scale-adjust should show current accumulated scale factor

[Drew Adams]

> C-x C-= runs the command text-scale-adjust.
> 
> It should give some feedback, in the minibuffer,
> about the current accumulated scale factor etc.
> E.g., the user repeats the command using '=', but nothing on the screen
> changes until each fifth '='. In the meantime a running tally of the
> current accumulated scale factor could be shown in the minibuffer so the
> user knows the command is indeed doing something.
> 
> Also when the fonts get bigger (e.g., every fifth '=') have a message
> saying what new font has been used.

Dunno if this responds to your request, but the mode line shows
(in the minor-mode lighter area) +1, +2, +3, or -1, -2, -3, when
you scale up or down.