cssimage: Implement (most of) current cross-fade syntax
cssimage: Implement (most of) current cross-fade syntax

The CSS4 spec adapted their cross-fade syntax again. Yay!
(The previous parser was completely broken anyway...)

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