colorbutton: don't hardcode a 16px margin around the color sample
colorbutton: don't hardcode a 16px margin around the color sample

Since themes might want different paddings around the color sample
according to where it's being used, don't hardcode a 16px one here.
The theme can specify a padding to get the same effect.

Reported by Christian Persch <chpe@gnome.org>

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