bug#2504: 23.0.90; new-frame => "no font backend available."

David Abrahams wrote:
> I think MacOS Emacs isn't very resilient to customizations for other
> platforms that should be ignored.  For example, my
>
>   default-frame-alist
>
> is 
>
>   ((menu-bar-lines . 1) (font-backend . "xft") (font . "Bitstream Vera Sans Mono-10.5") (tool-bar-lines . 0))
>
> But `M-x new-frame' causes emacs to report "no font backend available"
> without opening a new window.
>   

This is no different than setting (font-backend . "garbage") on any 
platform. If you have platform specific settings in your .emacs which 
you want to share between platforms, then you need to make them conditional.