GtkSeparator: Set orientable style classes initially
GtkSeparator: Set orientable style classes initially

This was an omission, horizontal/vertical would only be set
when the orientation is changed.

Lyude/gtk-,Adamovskiy/gtk,grubersjoe/adwaita,chergert/gtk,chergert/gtk,alexlarsson/gtk,Lyude/gtk-,davidgumberg/gtk,chergert/gtk,alexlarsson/gtk,jessevdk/gtk,jigpu/gtk,grubersjoe/adwaita,grubersjoe/adwaita,jadahl/gtk,jigpu/gtk,ahodesuka/gtk,jadahl/gtk,ahodesuka/gtk,Adamovskiy/gtk,Adamovskiy/gtk,jigpu/gtk,ahodesuka/gtk,Lyude/gtk-,davidgumberg/gtk,jadahl/gtk,davidgumberg/gtk,chergert/gtk,alexlarsson/gtk,davidgumberg/gtk,grubersjoe/adwaita,alexlarsson/gtk,alexlarsson/gtk,davidgumberg/gtk,ahodesuka/gtk,grubersjoe/adwaita,jessevdk/gtk,jadahl/gtk,davidgumberg/gtk,grubersjoe/adwaita,Adamovskiy/gtk,chergert/gtk,jigpu/gtk,Adamovskiy/gtk,ahodesuka/gtk,grubersjoe/adwaita,davidgumberg/gtk,davidgumberg/gtk,alexlarsson/gtk,ahodesuka/gtk,ahodesuka/gtk,jessevdk/gtk,jadahl/gtk,alexlarsson/gtk,Adamovskiy/gtk,jadahl/gtk,Lyude/gtk-,grubersjoe/adwaita,chergert/gtk,Adamovskiy/gtk,jessevdk/gtk,jigpu/gtk,chergert/gtk,jigpu/gtk,jessevdk/gtk,jigpu/gtk,jigpu/gtk,chergert/gtk,jadahl/gtk,Lyude/gtk-,Lyude/gtk-,Adamovskiy/gtk,jessevdk/gtk,jadahl/gtk,ahodesuka/gtk,Lyude/gtk-,jessevdk/gtk,alexlarsson/gtk,Lyude/gtk-