Theme generator (was: solarized)

[Stefan Monnier]

> Henrik tried to do it with emacs-doom-themes
> ( https://github.com/hlissner/emacs-doom-themes ) but apparently the theme
> generation part is not really good and he has been trying to find time to
> rewrite that part. But using that API to define a theme seems really easy :
> https://github.com/hlissner/emacs-doom-themes/blob/master/themes/doom-one-theme.el
>
> I think this is the kind of helpers that would warrant upstream integration :

Indeed, it seems that if we extended the `defface` machinery to allow
evaluation of Elisp code, we could make this "standard".


        Stefan