GtkCssProvider: Transform custom colors to a @define-color rule.
GtkCssProvider: Transform custom colors to a @define-color rule.

Given there are other rules such as @import (which will be supported),
keep a sane namespace here, so for (re)defining a color name, in the CSS
file it will look like:

@define-color color-name #fff;
@define-color other-color mix (@color-name, #f00, 0.4);

Adamovskiy/gtk,ebassi/gtk,chergert/gtk,davidt/gtk,Lyude/gtk-,ebassi/gtk,msteinert/gtk,jigpu/gtk,Distrotech/gtk2,Distrotech/gtk2,davidt/gtk,grubersjoe/adwaita,davidgumberg/gtk,davidgumberg/gtk,Sidnioulz/SandboxGtk,jadahl/gtk,ahodesuka/gtk,Sidnioulz/SandboxGtk,msteinert/gtk,ebassi/gtk,jessevdk/gtk,Distrotech/gtk2,bratsche/gtk-,davidt/gtk,davidt/gtk,simokivimaki/gtk,Sidnioulz/SandboxGtk,alexlarsson/gtk,bratsche/gtk-,alexlarsson/gtk,Adamovskiy/gtk,chergert/gtk,Distrotech/gtk2,Distrotech/gtk2,jadahl/gtk,Adamovskiy/gtk,jadahl/gtk,jessevdk/gtk,jessevdk/gtk,ebassi/gtk,grubersjoe/adwaita,jadahl/gtk,ahodesuka/gtk,Sidnioulz/SandboxGtk,Lyude/gtk-,Adamovskiy/gtk,Sidnioulz/SandboxGtk,bratsche/gtk-,jigpu/gtk,Adamovskiy/gtk,ebassi/gtk,grubersjoe/adwaita,jigpu/gtk,davidgumberg/gtk,Adamovskiy/gtk,msteinert/gtk,bratsche/gtk-,ahodesuka/gtk,simokivimaki/gtk,grubersjoe/adwaita,davidgumberg/gtk,jessevdk/gtk,davidgumberg/gtk,alexlarsson/gtk,chergert/gtk,Lyude/gtk-,msteinert/gtk,ahodesuka/gtk,Lyude/gtk-,Sidnioulz/SandboxGtk,ahodesuka/gtk,jessevdk/gtk,bratsche/gtk-,jigpu/gtk,davidt/gtk,Lyude/gtk-,grubersjoe/adwaita,Lyude/gtk-,jigpu/gtk,chergert/gtk,jessevdk/gtk,alexlarsson/gtk,chergert/gtk,grubersjoe/adwaita,grubersjoe/adwaita,simokivimaki/gtk,simokivimaki/gtk,chergert/gtk,ahodesuka/gtk,ahodesuka/gtk,Lyude/gtk-,davidgumberg/gtk,Adamovskiy/gtk,alexlarsson/gtk,jadahl/gtk,msteinert/gtk,grubersjoe/adwaita,jadahl/gtk,davidgumberg/gtk,ahodesuka/gtk,Adamovskiy/gtk,davidt/gtk,alexlarsson/gtk,simokivimaki/gtk,Distrotech/gtk2,alexlarsson/gtk,davidgumberg/gtk,chergert/gtk,jigpu/gtk,msteinert/gtk,Lyude/gtk-,jigpu/gtk,jigpu/gtk,alexlarsson/gtk,simokivimaki/gtk,jadahl/gtk,jessevdk/gtk,chergert/gtk,bratsche/gtk-,ebassi/gtk,jadahl/gtk