bug#3042: 23.0.92; display-visual class doc

[Drew Adams]

> I've now changed the section to this:
> 
> @defun display-visual-class &optional display
> This function returns the visual class for the screen.  The value is
> one of the symbols @code{static-gray} (a limited, unchangeable number
> of grays), @code{gray-scale} (a full range of grays),
> @code{static-color} (a limited, unchangeable number of colors),
> @code{pseudo-color} (a limited number of colors), @code{true-color} (a
> full range of colors), and @code{direct-color} (a full range of
> colors).
> @end defun

Thanks; that helps, I think.

> I think that's probably somewhat correct, although I'm not sure what
> `pseudo-color' really is.  Anybody?

Someone else?