frame: make sure to allocate the CSS border width
frame: make sure to allocate the CSS border width

Similar to GtkNotebook, GtkFrame was only allocating space for the
padding width, and not the border.

This could be seen by just running tests/testframe. With a theme that
renders frame borders, setting xthickness = 0 in the test draws the
button border over the frame border, which is wrong.

https://bugzilla.gnome.org/show_bug.cgi?id=664342

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