PaletteWindowWidget: set border width to make outer space in the container - SL #4295
PaletteWindowWidget: set border width to make outer space in the container - SL #4295

In the palette reimplamentation, commit 48ad255a, set_border_width was
removed.  Add it again to the corresponding widget, and get the value
from the theme.  Previously the value was given by:
self.get_style().xthickness .  Now we can use the widget border.

Signed-off-by: Manuel Quiñones <6f5069c5b6be23302a13accec56587944be09079@laptop.org>
Acked-by: Simon Schampijer <088e16a1019277b15d58faf0541e11910eb756f6@laptop.org>

i5o/sugar-toolkit-gtk3,samdroid-apps/sugar-toolkit-gtk3,sugarlabs/sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,puneetgkaur/sugar-toolkit-gtk3,sugarlabs/sugar-toolkit-gtk3,manuq/sugar-toolkit-gtk3,manuq/sugar-toolkit-gtk3,godiard/sugar-toolkit-gtk3,tchx84/debian-pkg-sugar-toolkit-gtk3,puneetgkaur/backup_sugar_sugartoolkit,godiard/sugar-toolkit-gtk3,godiard/sugar-toolkit-gtk3,tchx84/sugar-toolkit-gtk3,puneetgkaur/backup_sugar_sugartoolkit,puneetgkaur/sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,Daksh/sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,tchx84/debian-pkg-sugar-toolkit-gtk3,ceibal-tatu/sugar-toolkit-gtk3,ceibal-tatu/sugar-toolkit-gtk3,Daksh/sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,puneetgkaur/sugar-toolkit-gtk3,i5o/sugar-toolkit-gtk3,tchx84/sugar-toolkit-gtk3,tchx84/sugar-toolkit-gtk3,i5o/sugar-toolkit-gtk3,i5o/sugar-toolkit-gtk3,puneetgkaur/backup_sugar_sugartoolkit,tchx84/debian-pkg-sugar-toolkit-gtk3,ceibal-tatu/sugar-toolkit-gtk3,samdroid-apps/sugar-toolkit-gtk3,sugarlabs/sugar-toolkit-gtk3,samdroid-apps/sugar-toolkit-gtk3,Daksh/sugar-toolkit-gtk3,manuq/sugar-toolkit-gtk3,samdroid-apps/sugar-toolkit-gtk3