Fix drawing of gap on palettes attached to widget - Fixes #4776
Fix drawing of gap on palettes attached to widget - Fixes #4776

In Gtk 3.10, Gtk.Window is drawing a gray border around the palette.
This patch draw a black rectangle defore we draw Gtk.render_frame_gap
to draw the border but with a gap to connect to the attached widget.

Signed-off-by: Gonzalo Odiard <aef65ed16d0ea9f2366d05ae21f0b27430ef2e79@sugarlabs.org>

quozl/sugar-toolkit-gtk3,godiard/sugar-toolkit-gtk3,puneetgkaur/sugar-toolkit-gtk3,i5o/sugar-toolkit-gtk3,tchx84/debian-pkg-sugar-toolkit-gtk3,Daksh/sugar-toolkit-gtk3,tchx84/sugar-toolkit-gtk3,godiard/sugar-toolkit-gtk3,puneetgkaur/backup_sugar_sugartoolkit,sugarlabs/sugar-toolkit-gtk3,i5o/sugar-toolkit-gtk3,sugarlabs/sugar-toolkit-gtk3,puneetgkaur/backup_sugar_sugartoolkit,puneetgkaur/sugar-toolkit-gtk3,tchx84/debian-pkg-sugar-toolkit-gtk3,Daksh/sugar-toolkit-gtk3,puneetgkaur/sugar-toolkit-gtk3,i5o/sugar-toolkit-gtk3,i5o/sugar-toolkit-gtk3,sugarlabs/sugar-toolkit-gtk3,tchx84/sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,godiard/sugar-toolkit-gtk3,tchx84/sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,tchx84/debian-pkg-sugar-toolkit-gtk3,quozl/sugar-toolkit-gtk3,puneetgkaur/backup_sugar_sugartoolkit,Daksh/sugar-toolkit-gtk3