GtkFlowBox: Set orientable style classes initially
GtkFlowBox: Set orientable style classes initially

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

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