spinbutton: don't render an additional background below arrows
spinbutton: don't render an additional background below arrows

It's an entry, so it already has a background below, even when the entry
doesn't have a frame. Also, gtk_spin_button_draw_arrow() will render a
background and a frame in the arrow space anyway.

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